HAWAII KAI (HawaiiNewsNow) - Hanauma Bay was closed Sunday after divers found what was described as a military device containing phosphorous, usually dropped from aircraft to mark locations with smoke.
Authorities initially thought that it was possibly an explosive device and shut down the park after it was discovered at around 9:30 a.m.
"We were told by some passer bys, some people who work with the program actually, that some divers had found this ordnance out there in the area called Witches Brew," said Honolulu Fire Capt. Earle Kealoha. "They brought it to the lifeguard tower, and that's when 911 was activated."
Military explosives experts from Schofield Barracks were sent to the bay to try to dispose of the device. A first attempt caused smoke, but failed to destroy the device.
"We were in the gift shop looking at postcards and everything, and all of a sudden we heard the 'bang,'" said visitor Donna Johnston of British Columbia, Canada, "And so we rushed over to the embankment and saw the red flame and the smoke going up the hill."
Johnston wasn't able to get down to the beach for a planned day of swimming and snorkeling.
"We were there (at the gift shop) for ages," Johnston said. "They said oh, it'll be just another half hour, then three fourths of an hour, and finally they said the military had to go back and get a different crew."
The Fire Department said the military's disposal team suggested keeping people at least a hundred feet away from the device.
"We advised the Hanauma Bay director of the situation, but its up to them as far as what they decided to do, and I believe again they decided -- they erred in the realm of safety, and decided to shut down the entire park," Kealoha said.
It was unknown when the park would reopen, but authorities said it would be likely the park would not open at all Sunday.
Stay with Hawaii News Now for any updates.