A chunk, or pieces, of concrete fell from the underside of the H-1 airport viaduct yesterday onto the townbound lanes of Nimitz Highway, but transportation officials inspected the elevated roadway and say it is safe.

No vehicles were hit and nobody was hurt when concrete fell onto the middle of three lanes of Nimitz Highway shortly after 2 p.m.

"We don't know if it was one piece or pieces," said Scott Ishikawa, spokesman for the state Department of Transportation. "The biggest piece was about one square foot."

Department of Transportation officials closed the middle lane between Pai'ea and Ohohia streets, and workers went up in a cherry picker to whack at the viaduct with a hammer looking for more loose concrete, Ishi-kawa said.

"There's no problem with the structure or the foundation," Ishikawa said. "The problem was restricted to the exterior portion."

The lane was reopened at 6 p.m.

Workers may return to secure with epoxy any loose pieces of the viaduct they may find, Ishikawa said.

"Over time, with the vibrations of traffic, there might be a chance that the exterior concrete may shake loose," he said. "It shouldn't be a problem."

Although the viaduct poses no hazard, Ishikawa said, DOT officials took extra precautions yesterday following its experience last month when a military truck carrying a crane crashed into the freeway's 'Aiea pedestrian overpass.

The crash — and subsequent inspection and dismantling of the overpass — caused thousands of drivers to be stuck in pau hana gridlock, some into the early hours of the morning.

"After the incident with the overpass, we aren't taking any chances," Ishikawa said.

Reach Dan Nakaso at dnakaso@honoluluadvertiser.com.