Firefighters were forced back while they were working a fire on Carlton Street, near the Buffalo Niagara Medical Campus, in downtown Buffalo.
Fire started about midnight. Once firefighters got there, they saw heavy flames rolling out of the back of the house.
No one was inside, but Division Chief Michael Tuberdyke said this fire seemed strange.
"Saying it's a vacant building and there was no power, I would say suspicious is a good word to use," Tuberdyke said.
No one was hurt.
Firefighters say the house was a total loss.