AUBURN — Authorities are investigating the cause of a fire near railroad tracks spanning the Androscoggin River on Tuesday morning, Battalion Chief Don Flanagan of the Auburn Fire Department said.

Firefighters responded shortly after 9 a.m. to a call of used railroad ties burning next to railroad tracks. The blaze had spread from a small brush fire about 10 feet away and was extinguished in 20 minutes, Flanagan said.

The cause of brush fire is under investigation by the Maine Forest Service and Auburn Police Department.

The ties, which had been left there by Pan-Am Railways, had little damage, Flanagan said.

A tanker from Auburn Public Works and portable pumps used river water to extinguish the fire.

Smoke billows from a fire in a stack of railroad ties beside railroad tracks before the trestle spanning the Androscoggin River between Lewiston and Auburn on the Auburn side. Russ Dillingham/Sun Journal