Origin of large boom in Highland Park unknown

HIGHLAND PARK, Calif. Eyewitness News received calls about the boom at 8:02 p.m., with locals reporting a loud noise near North Avenue 52 and Monte Vista Street. Some thought it was an explosion.

Firefighters responded but couldn't figure out what caused the sound.

There have been some similar incidents recently in Portland, Oregon, which turned out to be a pipe bomb exploding, but firefighters say there's no evidence to show that's what happened in Highland Park.