Chunks of concrete that fell from the H-1 Freeway viaduct are spurring safety concerns.
State Department of Transportation officials say they checked out the site and believe it is structurally safe.
But others aren't convinced.
Witnesses say a large block of concrete fell from the overpass onto Nimitz Highway across from Thrifty car rental around noon Saturday.
"It sounded like a car crash. We thought there was an accident," said witness Dani Ishikawa.
The concrete damage was caused by corrosion and engineers say it could be a sign of a bigger problem.
"We got to be very careful of spalling overhead because if there is pedestrian activity underneath or property, we have to cordon it off until we fix it because again, falling concrete can be very dangerous," said Panos Prevedouros, professor of Civil Engineering at the University of Hawaii at Manoa.
Spalling is caused by rusting reinforcement steel that expands, breaking the exterior concrete.
No one was injured by the falling concrete. But Ishikawa says the slab just missed a homeless man who sleeps in the area.
"That's quite a danger especially if the guy is just sitting there and it hits in the head. It's gonna probably put it out or hospital,” said bus rider Stephen Roddy.
On Thursday, rebar and a metal plate was still exposed where the concrete appeared to have fallen from. It also appeared as if other areas above the busy highway are deteriorating as well.
"It puts DOT in a rush to go and investigate the whole viaduct because there may be spalling elsewhere," Prevedouros said.
But DOT spokesman Tim Sakahara said that previous investigations conducted at least every two years determined the structure is safe.
"HDOT engineers inspected the site after receiving the call Saturday ... and will continue to inspect the area. Crews will perform maintenance work as necessary," he added.
In the past, Hawaii has received poor ratings for bridge inspections and maintenance. A national transportation research group says 6 percent of Hawaii's bridges are structurally deficient.
Regulars say they see lots of spots at the H-1 viaduct that concern them.
"The airport is actually a little bit worse than this place, it's really falling apart underneath," Roddy said.
Added Prevedouros, "Usually we identify spalling under a routine maintenance because it takes a while for the concrete to deteriorate. I don't know how often they inspect that area. But now, they have evidence that inspection is needed ASAP."