It happened around 10:15 a.m. at a home along the 10400 block of Lincoln Way West in Peters Township.
The fire chief says it took crews only about 15 minutes to put out the blaze, which was ruled accidental due to an electrical problem.
"Electrical wiring, I mean, it's just one of those things. It was an older home. There had been some upgrades over the years, but wiring does eventually all break down over time," said Fire Chief Dale Carbaugh, of the Mercersburg Montgomery Peters and Warren Volunteer Fire Department.
He says most damage is on the first floor of the home, although some of the second floor is damaged.
"The home sustained some pretty moderate damage on the first floor," Carbaugh said. "We had to open the walls up, that sort of thing. The contents had pretty much been destroyed inside the first floor. Structurally it is still sound. The homeowners will be able to rebuild there."
The chief says the home is not livable at this point.
"There are a lot of friends and family there right now," Carbaugh said. "When we left there shortly after noon, they were there already starting to clean up and getting ready for the re-build process."
The two people who live in the house were not home when the fire broke out.
No injuries were reported. The fire marshal is investigating.
Copyright 2015 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.