PUNA, BIG ISLAND (HawaiiNewsNow) - Lava from active fissures near the Leilani Estates subdivision has completed a nearly 4-mile crawl to the coast of Hawaii Island and is pouring into the ocean at two separate points. But a new crack could divert some of the flowing lava back underground.
Emergency management officials first confirmed around 11 p.m. Saturday night that lava from fissure 20 reached the ocean.
Hawaiian Volcano Observatory officials also reported sulfur dioxide levels have tripled, and they are reminding residents to take precautionary steps to limit exposure.
The elevated levels were detected in the Kamaili, Seaview and Malama Ki neighborhoods.
As the flow marched toward the ocean, a crack opened under the east lava channel early Sunday morning.
Officials say the crack was, at one point, diverting the lava from the channel into underground voids.
"This may cause changes downslope in the channel system and the ocean entry," HVO staff said.
Still, scientists say the flow entering the ocean shows no signs of slowing any time soon.
"We did see this same thing, the same type of thing, in the Kamoamoa eruption in 2011 and the lava that poured into ground never reappeared to surface and it's possible that could happen again but we are not sure," Wendy Stovall of the USGS said.
As the flow pours into the water and creates new land, officials are issuing new warnings about the threat for laze, the steam-like substance that rises from the ocean as it comes into contact with lava.
In addition, a critical access point to lower Puna communities was cut off when lava reached Highway 137 around 10:30 p.m. The 20-foot high wall of lava crossed the road just south of the 13-mile marker, shutting down parts of the highway and forcing police to implement roadblocks.
Highway 130 is currently only open to residents, and has already begun developing cracks. Metal plates have been installed, resulting in weight limits for motorists using that route.
The highway closure is expected to impact thousands of residents trying to get in or out of the lava-affected areas.
WATCH: Fissure 20 spewing lava in Lanipuna Gardens:
For most of the day Saturday, powerful rivers of lava threatened homes and roads in the lower Puna area as they continued traveling downslope toward the ocean, and just before 7 p.m. Saturday night, Civil Defense officials said brush fires that had been ignited by lava were forcing evacuations for residents along Kamaili Road.
Officials went door-to-door to clear the area and they are asking everyone to stay away until further notice. There are now three shelters open on the Big Island for those who do choose to evacuate.
On Friday, four people were airlifted to safety and at least four homes were destroyed in lower Puna as activity from fissure 20 increased. That activity continued Saturday as new fissures and older ones continued their explosive lava flows, spitting out towering lava fountains that lit up the night sky and set off thunderous gas explosions that could be heard for miles around.
On Friday evening, civil defense officials said a fast-moving lava flow had crossed Pohoiki Road and was threatening an isolated area with at least 40 homes.
Since the eruptions started more than two weeks ago, some 22 fissures have opened in lower Puna, claiming at least 44 structures in the Leilani Estates and Lanipuna Gardens subdivisions.
The eruptions took a particularly dangerous turn on Friday, with at least five separate fissures spitting out fresher, hotter lava from Kilauea's summit.
"With fresher, hotter magma, there's the potential that the lava flows can move with greater ease and therefore cover more area," said Janet Babb, USGS geologist, earlier in the day.
The incredible eruptive activity, which has been ramping up in recent days, comes as geologists say it remains unclear how long the eruptions will last.
Scientists have confirmed, though, that lava now spewing into lower Puna is new — from the quickly-emptying lava lake at Kilauea's summit crater some 20 miles away. The first eruptions into lower Puna were sending older lava from a 1955 flow into the community.
Residents, meanwhile, say the volcanic activity is taking a huge toll — day by day.
"It's been like hell," said resident Ikaika Marzo, who has been helping get much-needed information to those in lower Puna.
He described the sounds of lava in the area as 10 or 20 jets taking off at once and right in your backyard. "It's like huge grenades going off," he said. "It shakes the whole community."
The ongoing volcanic activity prompted civil defense authorities to urge extreme caution for anyone still in lava-ravaged areas.
"Leilani Estates evacuees must be alert to possible decreased availability of access," civil defense authorities said. "No access is allowed at his time for residents of Lanipuna Gardens due to high levels of dangerous volcanic gases.
Meanwhile, authorities continue to closely monitor activity at Kilauea's summit crater, where an explosive eruption early Saturday spewed ash into the air.
They're urging residents across the Ka'u District and Puna to be prepared for rapid changes in air quality because of the potential for ashfall or higher concentrations of sulfur dioxide.
On Thursday, heavy vog across lower Puna forced school closures. But the return of winds Friday meant volcanic emissions weren't leading to high concentrations of sulfur dioxide.
Jim Kauahikaua, USGS geophysicist, said the amount of gas spewing from outbreaks in Leilani Estates and nearby Lanipuna Gardens is about the same as the amount that comes out of Halemaumau Crater. The difference? The crater isn't in the middle of residential communities.
"The thing to remember is this is putting out as much sulfur dioxide as Halemaumau does normally," he said.
Geologists are also monitoring widening cracks in a number of roadways in Leilani Estates, ground zero for the ongoing eruptions.
Steve Brantley, of the USGS, said the large cracks, which have torn roads apart in some places or created gaps of 1 yard or wider, are an indication that magma is continuing to enter the rift zone.
"The rift zone is being forced apart," he said. "I think clearly it points to the potential for additional eruptive activity" in lower Puna.
Marzo said he saw a crack on Nohea Street widen from about 3 feet on Thursday morning to about 10 feet wide later in the day. He also said that about 40 yards of the road sank.
"These cracks are definitely taking a toll on people getting to their homes," he said.
The developments underscore the scope of the disaster in the area, which has upended lives, destroyed homes and shows no signs of stopping.
In lower Puna, residents say the eruptions have turned their community into a "war zone."
"Everything is so uncertain. It's really nerve-wracking," said Debbie Kalaluhi, who can see the ongoing eruption of fissure no. 17 from her backyard. "You're very on edge. You have to really see it to believe it."
Mandatory evacuations remain in place for the Leilani Estates and Lanipuna Gardens subdivisions, home to about 2,000 people, but not everyone has heeded them and authorities haven't forced people to leave.
About 300 people are staying at three American Red Cross emergency shelters, while hundreds more residents are staying with friends and family.
Talmadge Magno, Hawaii County Civil Defense administrator, said Thursday that about 20 homes remain occupied in Leilani Estates — a fact that he expects will change as volcanic activity continues to cut off roads, gobble up utility lines and send toxic fumes into the air.
"Lava has a way of moving people," he said.
Meanwhile, authorities continue to urge thousands living elsewhere in Kilauea's east rift zone to be prepared to evacuate quickly.
A presidential disaster declaration has been issued for the ongoing Kilauea eruptions, which have changed the landscape of a Big Island community, destroying dozens of homes, covering roads and gobbling up utility lines.
Tina Neal, USGS scientist-in-charge at the Hawaiian Volcano Observatory, has said there's no's telling how long the eruptions will continue.
► LIST: Lava threat forces evacuations, closures
► Big Island businesses face layoffs, losses as visitor cancellations mount
► Satellite images help tell the story of lava's destruction on Big Island
► 'Dead or dying': Lava, toxic gas decimate crops in lower Puna
► From horses to bunnies, mission underway to rescue pets in lava-ravaged zones
► Here's how to help those affected by the Big Island eruptions
Authorities have compared the eruptions of Kilauea along the south rift zone to volcanic activity in February 1955, in which at least 24 separate volcanic vents opened up and lava covered about 3,900 acres.
Back then, coastal communities from Kalapana to Kapoho were evacuated and "sections of every public road to the coastline were buried by lava" before the eruption abruptly stopped in May 1955.
The last time lava threatened Puna was in 2014, when a flow closed roads for weeks in Pahoa, forced evacuations and claimed several structures, including one home.
This story will be updated.