ORONO, Maine — A small fire Friday night at a University of Maine fraternity has been ruled an arson, an official from the state fire marshal’s office said Saturday.

“The cause was intentional human element,” Sgt. Joel Davis of the fire marshal’s office said.

Davis said the fire remains under investigation by fire marshal’s office investigators and local police.

No one had been charged in connection with the arson as of Sunday, Orono fire Lt. Bryan Hardison said. He said that investigators so far have only been able to interview one of the people who were at the house.

Hardison said the others will be interviewed in the week ahead, a process that could take several days because of class schedules and because the students have dispersed.

The fire at the Phi Kappa Sigma house on College Avenue began about 11 p.m. and was quickly extinguished by the house’s sprinkler system, Orono fire Lt. Joel Sides said.

He said that fire damage was contained to the attic and that no one was injured.

The fire prompted the evacuation of 15 UMaine students and the temporary closure of College Avenue.

UMaine spokeswoman Margaret Nagle said Saturday that she was told that the fire started in a small mattress on the third floor, which includes some student living space and an attic.

The university offered the displaced students temporary accommodations, assistance that one student accepted over the weekend, Nagle said. The others found their own places to stay for the time being, she said.

Nagle said that the Pine Tree Chapter of the American Red Cross also offered assistance to those who need it.

Hardison said the students likely won’t be allowed to move back in this semester because of the extent of the water damage that occurred when the sprinkler system went off.

“It’s all the way from the attic to the basement,” he said, adding that while partial electricity has been restored, parts of the fraternity house might require rewiring.

Nagle said Sunday the university is offering the displaced students room and board through the end of the semester.