The fire was early Friday morning at an 84 Lumber facility in Luzerne County.
Firefighters cleared the scene in the morning but police were called to the place in the afternoon.
The story changed while workers were doing some cleanup after the early- morning fire.
Police said those employees noticed some tools were missing from the shelves. Police took a closer look and realized there was a break-in before the fire.
It was police who first discovered the flames at 84 Lumber near Pittston.
They said they were responding to a burglar alarm when they found the fire.
Firefighters said flames can set off a burglar alarm so the early ruling on the fire was accidental.
Officials with 84 Lumber said in the morning they believed it was an electrical fire that started in the bathroom.
Hours later workers cleaning up the mess noticed there were a bunch of tools missing. That's when police were called in. Local officers and state troopers were there to examine the scene.
They found evidence of a break-in. They found tools had been stolen. Now they're trying to determine exactly how that fire started so soon after the burglary.
The state police fire marshal is looking to see if the fire was intentionally set by the burglars or if the breakin itself caused something to catch fire.
Police said they are not ruling out anything.
Anyone with information about the breakin and fire at 84 Lumber is asked to call 911.