MILWAUKIE, Ore. - Investigators believe a two-alarm fire that heavily damaged a Milwaukie family's home Sunday night was likely caused by someone else's fireworks.

A passerby noticed heavy smoke and flames coming from a garage attached to the home at 1710 S.E. Oak Shore Lane and called 911 about 11:20 p.m., according to officials with Clackamas Fire District No. 1. Apparently the residents had already escaped safely when the passerby pounded on the front door and windows to alert them to the blaze.

When firefighters arrived, they were unsure if anyone was still inside and some searched the home while other crews attacked the fire. It took crews 45 minutes and 10 engines to put the fire out.

Investigators believe the fire started in the garage area and spread through the attic into the home. While the home is still standing, investigators said the damage inside will be difficult to repair.

Neighbor Susan Keil said she wasn't surprised to hear that fireworks likely sparked the blaze.

"There were some loud fireworks just before the sirens occurred," she said.

She was worried for other homes on Oak Shore Lane as well.

"There are a lot of big trees, and it's pretty dry here because of the heat," she said. "I was concerned about anything else catching fire ..."