OROVILLE, Calif. -- A highway overpass that was under construction collapsed early Tuesday, crushing a delivery truck and seriously injuring a construction worker who clung to a steel beam as it tumbled 50 feet to the ground.

Firefighters swarmed the FedEx delivery truck to cut its driver from underneath a large steel beam that crushed the hood but missed the cab. A second beam landed on the back of the truck.

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Rescuers freed the driver, Robert Sylvester, 45, of Chico, about 2½ hours after he was trapped. He suffered only a sprained ankle and minor cuts, his wife, Carol, told The Associated Press.

"We've gone from thinking he was absolutely the unluckiest person to the luckiest," Carol Sylvester said after bringing her husband home from Enloe Medical Center in Chico.

The construction worker, Jeffrey Doll of Olivehurst, fractured his pelvis, left elbow and lower left leg when the beam he was on collapsed around 7:15 a.m. Doll, 39, was listed in serious condition after being airlifted to Enloe Medical Center in Chico, hospital spokeswoman Sharon Cuglietta said.

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"He rode it 50 feet down to the ground. It's incredible that he's going to survive that one," said Mark Dinger, a spokesman for the California Department of Transportation.

The overpass was being built over highway 149 where it intersects with highway 70 in Butte County, about an hour north of Sacramento, CHP spokeswoman Karen Ogle said. The project began last summer and was scheduled to be completed in fall 2009.

"It's incredible that he's going to survive that one." - Mark Dinger, Caltrans

Highway 149 had been closed overnight and until 5 a.m. Tuesday while workers from private contractor FCI Constructors, Inc. of Benicia erected concrete columns and steel tubes weighing between 2,400 and 3,000 pounds that were held together with cables and steel I-beams, Dinger said.

FCI has no record of health and safety violations and a random inspection in July 2005 found no infractions, said Kate McGuire, a spokeswoman with the state Division of Occupational Safety and Health.

FCI President Curtis Weltz, who arrived at the site after the collapse, said he did not yet know what caused the structure to collapse.

"There's a bunch of different possible scenarios. It's never happened to us before," Weltz said.

Weltz said the company will release more details about the investigation as it develops.

"Safety is our top priority, and we are very concerned about this. We are working on site with Cal/OSHA and the California Department of Transportation to investigate the cause of the incident and will provide further information as we receive it," Weltz said in a statement on the company's Web site.

FCI is one of three companies cited by Cal-OSHA last summer for intentionally failing to report worker injuries while building an earthquake-proof replacement on the eastern span of the Bay Bridge in Oakland, NBC affiliate KCRA-TV in Sacramento reported.

Cal-OSHA fined the contractors $6,000.

Jacque Underdown, a spokeswoman for the project's second contractor, Granite Construction Co. of Watsonville, said the company was cooperating with state agencies leading the investigation.

Carol Sylvester said her husband -- a father of three who has worked for FedEx since 2003 -- began his delivery route driving north on highway 149.

"He saw something fall, he thought a box. Then things started hitting the truck," she said. "I think he's in shock and glad. It was a long time in the truck and he's glad to be home."

Robert Sylvester was resting at home on the couch within four hours of being pulled from the truck.

Construction crews planned to stabilize the remaining structure and remove an estimated 70 tons of steel worth about $50,000 that crashed onto the highway.

"The top priority right now is to stabilize this and get it reopened to traffic," Dinger said.

Meanwhile, FedEx was evaluating the "large number of packages" damaged in the accident.

"When it is deemed safe and all official investigations are complete, the packages will be retrieved and returned to our local facility," said spokesman Robert Boulware.

The Department of Transportation was directing drivers to use Highway 162 until the road could be reopened, possibly as early as Wednesday morning.

Near the overpass, a 29-year-old female driver was injured when her sedan collided with a Department of Transportation pickup. She suffered two broken femurs and a spokeswoman at Enloe Medical Center said she was in fair condition.