HOULTON – Houlton firefighters responded Tuesday to yet another fire of unknown cause.

At 5:20 p.m., a motorist driving on Cooks Brook Road spotted a fire in a storage building behind the home of Jerry Schools. The motorist notified the Schoolses, who were at home, and they called the fire department.

More than 20 firefighters responded with three fire trucks. They were on the scene for about an hour.

Fire Chief Milton Cone said Wednesday that the fire started outside at the rear of the roughly 12-foot-by-16-foot wooden structure which once had been used as a chicken coop.

A cause has not been determined, and the State Fire Marshal’s Office has been notified, he said.

Since July 26, the town has had five fires, including a warehouse, and two mobile homes, one of which was occupied, but the owners were not home.

So far, only the fire in the occupied mobile home has been determined to have been set intentionally. The others, including the one on Tuesday, remain under investigation and the causes have not been determined.