A train carrying liquefied propane derailed Monday morning, setting off an explosion and fire that forced evacuations from this small central New York city and shut down a section of highway.

The 7 a.m. blast sent a huge fireball into the dawn sky. Thick smoke continued pouring out hours later as about half a dozen propane tanker cars burned, said Police Chief David Meeker. He said the explosion followed the derailment of about 15 of the train's 80 cars.

Fire crews fought to keep the flames from spreading to other tanker cars, about half of which carried propane.

"There is danger of further explosions," said Fire Department Lt. Kevin Salerno.

There were no immediate reports of injuries or fatalities.

The derailment occurred in an unpopulated area on Oneida's north side. Officials were evacuating an area of about a one-mile radius, covering most of the downtown area of the city of 10,000. Up to 4,000 people live within that area, but the evacuation was mandatory only for homes closest to the blast.

A 23-mile stretch of the state Thruway, which passes within a mile of the explosion, was closed in both directions as a precaution, said Patrick Noonan, a spokesman for the Thruway Authority.

Amtrak suspended service between Syracuse and Albany.

The CSX Corp. train that derailed was headed from Buffalo to Selkirk, just south of Albany, said company spokesman Robert Sullivan. He said the cause of the accident hadn't been determined.

Sullivan said that in addition to propane, two cars were carrying hazardous materials. One contained a flammable liquid and the other carried a corrosive, but he had no other details on the materials.