A three-alarm fire displaced all those staying at the Budget Inn in South Portland Tuesday night. Sam Rogers, courtesy of South Portland Fire Department

A three-alarm fire that overtook the Budget Inn in South Portland Tuesday night was caused by a faulty electrical system, officials said.

Fire crews were called to the hotel, located at 634 Main St., at around 7 p.m., the South Portland Fire Department wrote in a post on social media.

No injuries were reported, but the blaze displaced all those who were staying at the motel, Deputy Chief Brian Smart said on a phone call. Nine rooms had been rented to couples and families Tuesday night, he said. Crews with the Office of the Maine State Fire Marshal were investigating after 10 p.m., he said.

An electrical failure in the ceiling of one of the hotel’s rooms sparked the fire, the department said in an update Wednesday afternoon. From there, flames spread through the attic and internal structure.

Smart spoke from the hotel Tuesday night, where he said investigators with the fire marshal’s office at were still on the scene at around 10:30 p.m., but “all the fire trucks have gone home to clean up.”

The fire reached three-alarm status, prompting mutual aid responses from around a half-dozen other departments, including Scarborough, Gorham and Westbrook, Smart said. Crews managed to extinguish it around 9 p.m., he said.

“Knowing how quickly an attic fire could spread, we called for additional resources early,” Fire Chief Phil Selberg said in a written statement.

The department had extinguished another fire at the hotel years ago, so several crewmembers were familiar with the building’s layout.