Firefighters from three departments responded Sunday to a fire behind Wal-Mart in Palmyra that was caused by a malfunctioning valve in a system that heats propane for the building, according to fire officials.

The fire occurred in a portable heater about 25 feet from the back of the building and did not affect the building itself, Newport Assistant Fire Chief Ricky Turner said Sunday night.

“There was no external damage to the building at all,” Turner said. “It was all kept in the heater.”

He explained that two little portable heaters behind the building heat propane from liquid to vapor to feed other heaters on the roof of the building and the furnace.

A passerby notified authorities of the fire around 3:58 p.m. Sunday after driving by the building and seeing flames, Turner said.

“When we got there, there was a whole lot of flames going on,” he said.

The Wal-Mart building was evacuated of customers and employees and was closed for the evening, Turner said. Some employees returned to the building later to do light stocking, he said.

About 30 firefighters from Newport, Pittsfield and Corinna responded to the scene, according to Turner. They cleared the scene around 6:45 p.m., he said.

He said there were no injuries in the fire.

He said when firefighters left the scene, Dead River Co. was there and the furnace was up and running again. He said a new heater would be installed within the next couple of days.

Amy Calder — 861-9247

acalder@centralmaine.com

Twitter: @AmyCalder17