Mars police are investigating an arson case following a fire last week that destroyed a house on the 300 block of North Garfield Avenue in the borough.

Police launched the investigation after Trooper DuWayne Baird, a fire marshal at the Butler barracks, ruled arson in the Thursday night blaze.

The fire had “multiple points of origin,” Baird said Monday in explaining his ruling.

Mars police Lt. Beau Sneddon said Monday that police have a suspect, but he declined to identify that person.

On Friday, police obtained an arrest warrant for the homeowner, 63-year-old Larry D. Stevick, stemming from a domestic dispute with his live-in girlfriend about 45 minutes before the fire.

He is accused of pushing, choking and kicking the victim about 9:15 p.m. Thursday. She suffered apparent minor injuries. As she was leaving the house, he allegedly kicked her dog.

District Judge Sue Haggerty issued the warrant for Stevick on charges of simple assault, harassment and animal cruelty.

However, Sneddon said police did not know of the alleged domestic case until after the fire, learning about the incident while investigating the blaze.

Police said authorities found Stevick “over an embankment immediately behind the residence” after the call for the fire. He was taken to a Pittsburgh hospital for treatment of injuries.

Sneddon said he did not know how Stevick suffered the injuries or the extent of them. He declined to say if police have spoken to Stevick or if he is a suspect in the fire.

According to the Butler County Assessment Office, Stevick purchased the house in November 2007. The home consists of a main floor, a large basement and an attic.

Adams Area Fire District firefighters were first on scene and reported heavy flames shooting from the structure. Al Minjock, assistant fire chief, said it took about an hour of heavy work to extinguish the fire.

Baird was eventually notified and he was on scene early Friday morning to begin his investigation. He estimated damage to the structure and contents at $250,000.

It was not immediately known if the property was insured.

Baird said he found most of the fire damage was on the first floor, with more than one point of origin.

“It appears the fire was started in multiple areas of the house,” he said.

Additionally, Baird noted, it appeared that motor oil had been poured “everywhere” in the basement. An empty large plastic jug of motor oil was found on the main floor.

“It's unclear as to why the oil was dumped everywhere,” he said.

Also unclear was if the oil or an accelerant of some kind was used to start the fire.

Sneddon said the investigation is ongoing.

“There's just a lot of moving parts,” he said. “A lot of people in that neighborhood. A lot of evidence that we're still working to gather.”