MEDFORD (AP) — The authorities say it appears a firebomb ignited the southeast Medford blaze that closed Interstate 5 for several hours on Sunday.

Medford police Lt. Tim Doney says fire inspectors found the device in the brush where the flames started.

Doney declined to provide specifics about the device, but it wasn’t fireworks. The device, which will be sent to a crime lab for analysis, was found about 1,000 yards south of a mobile home park.

The fire jumped I-5 about an hour after it began. It took about 100 firefighters, a water-dropping helicopter and a bulldozer to stop the flames. The fire also closed Highway 99.