AUBURN — A railroad tanker carrying a chemical used in papermaking derailed and slid down an embankment Tuesday, but fire officials said the accident did not create a public health threat.

The tanker carrying sodium hydroxide and a boxcar carrying corn slid down an embankment and were on their sides in the Danville Junction section of Auburn, said Deputy Fire Chief Robert DeWitt. A third car, a tanker, also jumped the tracks but remained upright.

The sodium hydroxide, or caustic soda, did not leak but DeWitt said vapors may have escaped when a valve was damaged during the accident. He said the chemical is not highly poisonous and that no evacuation was necessary.

Firefighters planned to return to the scene when Springfield Terminal Railroad crews removed the contents of the derailed cars. Cranes had begun arriving at the scene to upright the cars, said F. Colin Pease, spokesman for Guilford Transportation Industries, Springfield’s parent company.

The cause of the derailment was not known but officials suspect that the load of corn in other cars may have shifted, said Pease. He said the train was moving at 10 mph or less when the accident happened.

Pease said the train was bound for Portland.