Updated

Two freight trains that collided in an Oklahoma wheat field weren't blowing their horns or flashing their lights as they hurtled toward each other, according to long-haul trucker who watched helplessly from a highway as the locomotives collided head-on.

Three of the four crew members assigned to the trains were still missing Monday, and investigators feared they couldn't have survived the Sunday crash and tremendous fire. One crew member jumped from the slower-moving train before the accident and survived with scrapes and bruises.

The National Transportation Safety Board determined that one of the trains failed to take a side track and give the other locomotive the right of way, NTSB spokesman Mark Rosekind said Monday night. He declined to say which train was on the wrong track, but said no malfunction was found in the signals that guide the trains.

The collision happened Sunday morning just after an eastbound Union Pacific train carrying mixed goods from Los Angeles to Chicago passed through Goodwell at a good clip. A mile east of town, it hit a westbound Union Pacific train hauling cars and trucks.

The resulting diesel fireball merged tons of steel and spewed black smoke that could be seen for miles across the flat, arid landscape that makes up the Oklahoma Panhandle.

Long-distance truck driver Gary Mathews, hauling freight from Phoenix to Missouri along U.S. 54, had been running evenly with the eastbound train at 68 mph outside of Goodwell and looked ahead to see another train approaching on the same track.

"I was thinking, I'm going to see a train crash unless somebody does something," Mathews, of Independence, Mo., said Monday in a telephone interview with The Associated Press. "They're not blowing the horn to each other, blinking lights or whatever. I kept thinking, 'This cannot happen, it cannot happen.'"

The Union Pacific railroad has sidings at Guymon and Goodwell, but only a single track runs between the two communities about 300 miles northwest of Oklahoma City.

"One train had the right of way. We're still getting the data to figure out what was scheduled to happen. There was a side track and we're trying to figure out what was supposed to be where, and when," Rosekind said.

Mathews said he often will travel evenly with trains to see how fast they are going. "I like to run with the trains," he said.

Mathews said the westbound train slowed considerably before the crash, but the eastbound train was still traveling "65 or better" when the trains hit about 50 yards away from him.

"A blast of hot air came through the side glass, and it put a burn on you like you step out of an air-conditioned bar into 110 degrees, through the glass," he said. "There was a 'thud' and it was over. Smoke was rolling. Smoke went up so high it was like a foundry on fire, and it was barreling straight up," he recalled.

"After I seen it, the feeling went through me, it scared the tar out of me, and I didn't stop until I reached Emporia" in Kansas, about 350 miles away. He was interviewed Sunday by the Guymon Daily Herald newspaper and reached Monday by the AP.

"I didn't even stop," Mathews said, as he recalled watching the unfolding seconds immediately after the crash in his rearview mirror.

Freight train speeds are governed by the Federal Railroad Administration and depend on how a section of track is rated. The highest class of track allows speeds up to 80 mph. It wasn't immediately known how the track near Goodwell was rated.

Investigators hadn't yet been able to search the wreckage for any bodies.

"They have to let the metal cool ... to see if they can get in there and find the bodies of the missing, and that may never happen," said Betsy Randolph, a trooper with the Oklahoma Highway Patrol.

Firefighters did what they could to cool the freight cars, and a crew was dispatched from Fort Worth, Texas, to smother the flames with foam. The trains' engines seemed to merge in the collision.

"It was a tangled, mangled burning mess," Randolph said.

The United Transportation Union identified those aboard the trains as conductor Brian L. Stone, 50, of Dalhart, Texas; engineers Dan Hall and John Hall; and conductor Juan Zurita, who escaped virtually uninjured. The Halls are not related.

The track will likely need to be rebuilt before the line reopens.

"It will be a slight inconvenience," said Scott Robertson, the superintendent at Farmers Elevator Inc. "The wheat harvest is nearly done and I haven't seen anything at any of the elevators around here sending (wheat) out. It's going to delay some deliveries, but it's not going to have that much of an impact."

U.S. 54, which runs alongside the track, was closed for a time. Eastbound lanes reopened Monday morning, but westbound traffic was diverted for a few miles, Randolph said. Boxcars littered wheat fields surrounding the site.

Rosekind, the NTSB spokesman, said at a news conference Monday morning that investigators would be on the scene the rest of the week.

"Our mission is not only to determine what happened, but why. It's that why that allows us to make safety recommendations to prevent these kinds of accidents from occurring in the future," he said.

Union Pacific spokesman Tom Lange said the trains were equipped with data recorders, similar to those recovered following aircraft accidents.

Many freight lines don't run on a set schedule and the number of trains through an area can vary from day to day, said Rob Kulat, a spokesman with the railroad administration. He and railroad officials referred questions to the NTSB.

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Associated Press writer Ken Miller contributed to this report from Oklahoma City.