Fourteen people were killed when a barge he was towing rammed into the bridge Sunday morning.
Investigators with the National Transportation Safety Board interviewed Dedmon on Wednesday, said Brett Beuerman, spokesman for barge owner Magnolia Marine Transport Co. of Vicksburg, Miss.
"It went the way we thought it would go," Beuerman said Thursday. "There were no surprises."
Ken Suydam, the National Transportation Safety Board's investigator in charge of the accident, said tests showed no traces of illicit drugs in Dedmon's system.
"The Coast Guard records reveal no previous suspensions or violations on the captain's record," he added.
However, in the 42 hours preceding the accident, Dedmon had had less than 10 hours of sleep, Suydam told reporters.
"Nine-point-five hours of sleep, 32 hours of awake," he said. "He's asleep for 3.5 hours, he's awake for 14.5 hours, asleep for six. He's awake for five and the accident occurs."
The NTSB did interview the towboat's five other crew members, who said they tried to rescue victims but their skiff got caught in a load of hoses that spilled out of a tractor-trailer rig.
Suydam, who interviewed Dedmon Wednesday, said that the last thing Dedmon says he remembers before the crash was passing a marker in the river. That would have taken place about five minutes before the tug's barges hit the bridge.
"The limited information on medical history we have on him at this time does not reveal anything remarkable in those records," Suydam said.
Dedmon also said that he was conscious immediately afterward.
Meanwhile, the search for more victims of the accident has been called off. If there are any more bodies in the murky depths, divers can't seem to find them.
Transportation officials used the giant claw of a crane to hoist chunks of concrete and twisted rebar from the muddy river. Divers gave up on recovery Wednesday afternoon, calling it a salvage operation instead.
"They have exhausted every hot spot," said Lt. Brandon Kopepasah of the Oklahoma Highway Patrol.
He said he didn't believe there were any more bodies or cars in the water under the Interstate 40 bridge. Still, divers planned to stand by in case sonar detected anything.
The most recent victim pulled from the river was a 3-year-old girl, whose body floated a half-mile downstream. Rescuers found Shea Nicole Johnson of Lavaca, Ark., Wednesday morning. The bodies of her parents, Misty Johnson, 28, and James Johnson, 30, were recovered Monday.
The family was traveling to Tulsa when their car plummeted into the river through a 500-foot gap in the bridge about 40 miles from the Arkansas state line.
Oklahoma Highway Patrol Lt. Chris West said Thursday that nearly all of the victim's bodies have been returned to their families for funerals.
All of the victims except one, Army Capt. Andrew Clements, drowned, authorities said. Clements, who was traveling with his German shepherd to a new home in Virginia, died of blunt trauma to the head.
Skid marks on a section of the collapsed bridge don't stop before the edge. Witnesses said they saw at least one vehicle come to a screeching stop, then get shoved into the river by other cars.
One set of marks stretches about 300 feet. Authorities said those were from a truck driver who was able to back up from the edge.
Workers pulled 10 vehicles from the water, many of them mangled with busted-out windows.
State officials said it will cost about $15 million and take as long as six months to repair the bridge. They asked travelers to avoid far eastern Oklahoma.
Bruce Taylor, chief engineer with the Oklahoma Department of Transportation, said authorities are developing a plan to demolish the damaged portion of the bridge. He said his chief concern is how to remove an 800-ton span that collapsed on one of the barges.
"It's a very unique situation," Taylor said. "The piece that's hanging down will have to be demolished in place.
"I was surprised that the bridge steel could be twisted up and damaged like it was. It amazed me. I couldn't imagine the forces involved in causing that to happen," Taylor said.
Two bridge engineers from California who helped rebuild earthquake-damaged structures were dispatched to Oklahoma at the request of the Federal Emergency Management Agency to assist in rebuilding the bridge. Taylor said design changes are being planned to speed up the project.
"All of this is impacting how long it's going to take us to resume traffic on I-40," he said.
Signs along the interstate warn miles in advance that the road is ending, directing drivers onto winding two-lane highways through the hilly eastern Oklahoma farmlands of corn and cattle. Traffic snarls through tiny towns along the detour.