MARSHALL, Texas (AP) _ A 23-car freight train derailed when rain-weakened culverts collapsed Saturday, sparking explosions and a fire that shot 300 feet into the air and injuring four people, authorities said.

Two locomotives and 22 of the cars derailed, Union Pacific spokesman Tom LaHood said. He said the chemicals were not dangerous.

An evacuation was ordered in the heavily wooded area to the north and northwest, primarily because of threat of fire, said Fire Marshal Bill Elliott. Marshall is 152 miles east of Dallas and 22 miles west of Shreveport, La.

Ten families reportedly were evacuated, LaHood said from the company's headquarters in Omaha, Neb.

Heavy rains have drenched northeast Texas for the last several days, swelling some creeks and rivers from their banks.

The culverts built over one creek collapsed when the lead locomotive went over them, causing the locomotive to derail into a ditch alongside the tracks and piling up the other cars behind it, LaHood said.

''There was an area of track where there were four culverts that were visually inspected, and it was thought they would support the weight of the train, but they did not,'' LaHood said.

The derailment at 3:10 p.m. about five miles northwest of Marshall sparked a blast that shot flames up to 300 feet into the air, and several trees in the wooded area caught fire, officials said.

A witness, Mark Pope, who lives 300 yards from the scene, said he heard repeated explosions.

One car was empty, two contained non-regulated chemicals, and the rest carried alcohol products, LaHood said.

The chemicals, including denatured alcohol, propanol and ethyl hexanol, had been loaded at Texas Eastman's Longview petrochemical plant, a division of Rochester, N.Y.-based Eastman Kodak, Texas Eastman spokesman Jack Goodwin said.

Four crewmen, believed to be the only people aboard the train, were injured and taken to Marshall Memorial Hospital, where three were admitted. None of the injuries was life-threatening, a hospital spokesman said.