Law enforcement officials are investigating whether driver fatigue was a contributing factor in the I-70 truck crash that claimed two lives yesterday.

"At 3 o'clock in the morning, if you're not alert, it's easy to drift off the road. It appears it drifted off to the right," said Capt. Ed Clark, of the Colorado State Patrol.

The CSP's accident reconstruction team is assisting the Grand Junction Police Department with the investigation, Trooper Gilbert Mares said this morning.

"Well, we're definitely looking into the idea that driver fatigue was a factor because of the time of day and the circumstances preceding the crash. We're going to be discussing it a little bit further," Grand Junction police spokeswoman Lisa Bowman said today.

"One of the typical questions is was there driver fatigue, especially with long-haul truckers."

Bowman said the investigation is ongoing and no specific cause has been determined.

"We have not concluded that yet," she said.

Bowman said investigators would also investigate whether a medical condition was a factor.

"That would be part of our standard consideration in traffic accidents ... or if there were any substances like drugs and alcohol, though I don't think that's a factor," Bowman said.

The names of the victims and the trucking company have not been released.

One lane in each direction of Interstate 70 is now open.

The semi burst into flames after it knocked down a bridge column shortly before 3 a.m. Wednesday.

A spokesman with the Mesa County Coroner's Office said the victims are a man and a woman, both from Colorado.

Stacey Stegman, a spokeswoman for CDOT, said one westbound lane reopened at 6 a.m. today. An eastbound lane opened about 11 a.m. yesterday.

"We got a temporary repair," she said of the 26 11/2 Road bridge over the interstate on the north outskirts of Grand Junction.

The bridge, which has been stabilized with steel shoring, will remain closed, according to CDOT.

Stegman said trucks and local traffic should expect delays in the area.

Each day about 18,000 cars and trucks used that part of the highway.

Crews were working late Wednesday to install steel to repair all the north-side pier structure, including the column that was severed.

"We're still looking right now at what we can do for a more permanent thing," Stegman said.

Fire Battalion Chief John Williams said the semi burst into flames on impact, likely from the more than 300 gallons of diesel fuel in its tank, plus the 11 55-gallon drums of sodium hypochlorite it was transporting.