Honolulu rail officials say they’re investigating whether one of the project’s hauling trucks was following proper procedures when it hit an overhead sign on the H-1 freeway at the Kunia Road exit early Monday morning, spreading debris and prompting police to close lanes.

The accident happened at about 3:30 a.m. when a tractor-trailer hauling rail materials westbound, away from the H-1/H-2 interchange where the rail guideway is being built over the freeway, clipped the bottom of a freeway sign.

Honolulu police closed two lanes for more than an hour to investigate, slowing traffic. No injuries were reported.

The Honolulu Authority for Rapid Transportation released a statement Monday saying it is "looking into whether the contractor followed proper hauling procedures this morning to comply with height requirements along the freeway."

The truck belonged to Pineridge Farms, which is subcontracted by rail construction firm Kiewit Infrastructure West, officials said.

Cargo sticking up from the truck knocked a light off the sign, Pineridge Farms President Georgette Silva said. The driver didn’t realize what happened until a nearby motorist flashed his lights to alert him, Silva added. "This was an unusual piece," Silva said of the equipment that the truck was hauling. "It wasn’t a solid piece."

"We apologize for any damages and inconvenience to commuters caused by this morning’s incident," the HART statement said.