Investigators were unable to determine the cause of separate fires on consecutive days this week that damaged a pair of apartment buildings in Butler.

The fires on Liberty Street and on Center Avenue left at least a half dozen people homeless. No one was injured.

“Due to the extent of the damage, the cause of both fires is undetermined,” Trooper Duwayne Baird of the state police fire marshal’s office in Butler said today.

However, neither blaze appeared to be suspicious, he said.

The fire at 328 Liberty St. broke out shortly after 10 p.m. Sunday in a second floor storage room in back of the three-story, four-unit apartment building.

“There was something, possibly a radio, plugged in, in the room,” Baird said, suggesting the fire possibly was electrical.

Flames destroyed the storage room that was in back of the building, and forced several tenants to flee their apartments. Authorities said all four apartments were leased.

Butler firefighters quickly snuffed out the blaze but not before all the apartments had fire, smoke and/or water damage. A damage estimate was not available.

On Monday afternoon, fire erupted in the basement of three-story apartment building at 113 Center Ave., investigators said.

Jennifer Lacina, the lone tenant who lives there, discovered the fire after smelling smoke in the building.

Fire Chief Nick Ban said city firefighters extinguished the blaze quickly and minimized damage, estimated at $5,000, to the basement.

“The investigation found evidence of arcing in the ceiling of the basement,” Baird said.

The finding means that the cause for both fires may have been electrical, pending any new information.