RICHMOND — A fire that destroyed a portable outhouse at a construction site next to the Kennebec River was intentionally set, authorities said.

Richmond firefighters were called to a reported fire at the construction site at the under-renovation office building of the Richmond Utilities District at 9:57 p.m. Saturday. A crew of three firefighters, assisted by a Gardiner Rescue crew stationed in Richmond at the time, arrived and found a portable outhouse fully engulfed in flames, according to Richmond Fire Chief John Bellino.

“It was beyond being saved,” Bellino said of the plastic toilet structure. “It had started spreading to the vegetation around it, but (firefighters) were able to stop that by extinguishing the fire and knocking down what was spreading.”

Bellino said the Office of the State Fire Marshal was called in to investigate the fire.

Shannon Moss, spokesperson for the state Department of Public Safety, confirmed the fire marshal’s office is investigating and has deemed the fire to have been intentionally set.

Bellino estimated the value of the structure at about $600.

In October 2018, two teenage boys were charged with arson in connection to a fire that destroyed a portable outhouse at the town-owned Houdlette Field recreation area off High Street. Earlier that year the town temporarily closed its waterfront park bathrooms after repeated acts of vandalism to them. The park is next to the Richmond Utilities District office site where Saturday’s outhouse fire took place.

Moss said the cause of another, much larger, fire that took place over the weekend at Ron’s Auto Sales and Salvage on Route 17 in Washington is still under investigation by the fire marshal’s office.