Dangerous chemical bombs made from household materials have been left in mailboxes and front yards in Yucaipa over the past week, according to the San Bernardino County Sheriff's Department.
The bombs "often contain a chemical cleaner" along with tin foil inside a plastic beverage bottle. In a chemical reaction, the ingredients explode, the department said in a press release (PDF).
Nine such bombs have been found, sheriff's department spokeswoman Cindy Bachman said Wednesday.
No one has been injured, and no suspects have been identified, the department said in a press release issued Monday. Yucaipa, a city of about 52,000 residents, is about 10 miles east of San Bernardino.
The Yucaipa Police Department warned residents not to "touch, pick up or kick bottles filled with unknown fluids or objects." The police department said those who see such devices should get a "safe distance" from them and call 911 immediately.
The bombs "generally take a short time to go off" but sometimes don't explode until someone picks them up, the press release said.
Anyone with information about the bombs was asked to contact the Yucaipa Police Department at 909-790-3105.