CASTRO VALLEY -- Illegal fireworks thrown into a backyard by a passing car on Interstate 580 likely caused a small backyard fire in Castro Valley, a spokeswoman said.
Alameda County Fire firefighters responded to multiple reports of an explosion on Lobert Street around 6:20 p.m. and extinguished the fire within about a half-hour. The fire burned an area of about 15 feet by 5 feet.
No one was injured, and no structures were damaged, according to Aisha Knowles of the Alameda County Fire Department.
"Smoke was visible from 580," Knowles said. "There was some concern from drivers on the freeway."
Drivers called CHP to report that someone threw "something" over the sound wall.