DETROIT -- In the predawn darkness along a rural strip of track in Springfield Township, a pair of Canadian National freight trains smashed head-on, killing two men and trapping two others for hours in a fiery wreck that left investigators baffled, according to the Detroit Free Press.

Officials who gathered at the scene Thursday to retrieve bodies and douse a fire caused by 3,000 gallons of burning diesel fuel said the switch that moves trains to the side of a track to let another one pass could be at fault in the crash.

The switch, controlled by a remote station in Troy, moved train 533 headed from Durand to Detroit off the tracks to let train 243 pass as it traveled from Flat Rock to Flint.

In addition, investigators headed by the National Transportation Safety Board and the Federal Railroad Administration are investigating whether the rare head-on crash on the Grand Trunk Western rail line was caused by human error, equipment malfunction or fierce lightning Wednesday night.

The crash forced a five-hour evacuation of 100 homes in a rural area dotted by cornfields. Firefighters and hazardous-materials crews doused the blaze.

Two nearby schools, Andersonville Elementary School and Oakland Technical Center, were closed for the day.

When train 243 pulled out of Flat Rock early Thursday tugging hazardous gas, engineer Thomas Landris, 49, of Durand, and conductor Gary Chase, 58, of Owosso, were sitting in the front cab. The gas never leaked, railroad officials said.

As their 89-car train wound through the 55-m.p.h. stretch in Springfield, it is unclear whether the train from Durand to Detroit pulled back onto the tracks before Landris and Chase could pass, said Canadian National spokeswoman Gloria Combe.

Or the train may have stopped too far forward, jutting out in front of the oncoming train, she said.

Either way, Landris and Chase were dead moments later. Both men had worked for Canadian National for at least 30 years.

Chase's wife of 33 years, Barbara Chase, said a representative of the United Transportation Union told her family that a new computerized switching system may have played a part in the crash. Canadian National officials said the crash was under investigation.

"He wanted to make sure he survived to retirement," Chase said Thursday evening through tears. "Never got to Alaska. That was the first place we were going to go."

After hours of struggling, firefighters freed Allen Yash of Fenton and Jesse Enriquez of Detroit, who were taken by helicopter Genesys Regional Medical Center in Grand Blanc. Both were listed in critical condition Thursday night and Enriquez was being transferred to Detroit Receiving Hospital for treatment.

"I was breathless when I first walked up," said Scott Bickerstaff, a 21-year-old Groveland Township volunteer firefighter who was on the scene at 7 a.m. "You couldn't think of words to say. It was just a mangled mess."

Residents in the rural neighborhoods surrounding the crash were awakened early, some by anxious deputies pounding on their doors telling them to get out because of fears the trains were carrying hazardous material.

Canadian National plans to have the debris removed and trains running by today.

More clues to the collision may be found on event recorders aboard the trains, which are similar to the black boxes in airplanes. Communication between the dispatch center and the train is also recorded, said Peter Marshall, vice president of Canadian National's midwest division.

"We've had a tragic event this morning," Marshall said, adding that the investigation could take a few days. "We just don't have many of the facts at our disposal."

The trains were traveling in a 55-m.p.h. area, but it is unknown how fast they were traveling at the time of the crash, Canadian National spokesman Jack Burke said.

Head-on train collisions are rare. In 2000, there were nine head-on collisions, making up 0.3 percent of all accidents. No one was killed in those collisions and human error was found to have caused eight of them, according to the Federal Railroad Administration.

It will take from a few weeks to a year to release the crash findings, said Warren Flatau, spokesman for the Federal Railroad Administration.