Authorities began checking reports that tracks warped by the summer heat may have caused an Amtrak train to derail, injuring more than 160 people. About 200 stranded passengers were shuttled by air Saturday to their destinations.

The National Transportation Safety Board sent an investigation team to the site 50 miles south of the Canadian border where seven of the train's nine passenger cars left the tracks and overturned Friday.The train, dubbed the Empire Builder, was traveling at 79 mph, its authorized speed limit for the area, Amtrak officials said.

The investigators are to examine reports - including the observation of an engineer who said he tried to stop the train but couldn't - that 97-degree temperatures in the area had caused rails to warp or buckle. But the NTSB team also will look into all other possible causes, said Amtrak spokeswoman Marcie Larson.

"The safety board will investigate and it would be premature for us to make comments because it would be purely speculation," Larson said.

Some 200 passengers bound for Seattle and Portland, Ore., boarded a small shuttle plane Saturday afternoon in nearby Glasgow, Mont., for a short flight to Great Falls and were met by two DC-9s brought in from Oakland, Calif., and Las Vegas, Larson said.

The shuttle operation had to be adopted after earlier efforts to gain clearance for the DC-9s at an old Strategic Air Command airfield at Glasgow were unsuccessful, she said.

Three buses chartered by Amtrak left the Saco area at about 2 a.m.

with about 85 locally bound passengers, including one bus that went as far as Spokane, Larson said.

Meanwhile, Friday's eastbound Empire Builder, delayed in Havre to the west of the accident, finally passed through the site on a side track about 1:40 a.m. Saturday and continued east some 121/2 hours behind schedule, Larson said. She said the main track was not expected to be open until late Saturday.

"They rerailed the last two cars of the train overnight and were working their way forward trying to get things rerailed," she said.

The nine-car westbound train originated in Chicago and there were 361 passengers and 17 crew members aboard when the high-speed accident occurred, Amtrak spokesman Bruce Heard said.

"When I saw the bartender's eyes turn white, I knew we were in trouble," said Jeff Regan, of Dubuque, Iowa, who was handing over a $20 bill to the bartender at the time. "It just tipped over. It just kind of slid to a stop. It was all over in about 60 seconds."

Charlotte Tvedt, of Tacoma, Wash., said she felt a jerk and then the train "kind of turned on its side . . . there was nothing in the cabin but dust and rocks. My daughter was yelling and my grandson was crying, but other than that I think we kept pretty cool."

A total of 149 passengers were treated for back and neck injuries, cuts and bruises and another 15 were admitted to area hospitals, including two in serious condition, one sustaining a spinal cord injury and the other with a pelvis injury and a fractured jaw, Amtrak and hospital officials said.

Residents of the small town, who were outnumbered by the passengers, flocked to the site to offer assistance and put up 150 people in area homes, Larson said. Others were taken to shelters in Saco, Hinsdale and Glasgow, with most ending up at a Red Cross shelter set up at the Glasgow Civic Center. Many were fed at Saco High School.

"Seemingly the community has just opened their arms to these passengers," Larson said. "They've just really gone out of their way to help and have responded so well in this emergency situation."

Federal regulations require that the 17 crew members be tested for drug use, Heard said.

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