Spate of dry-ice bombs explosions in Long Beach, Calif.

A Long Beach, California, police officer was slightly injured Sunday after a crude dry-ice bomb exploded next to him in an alley near the Artesia (91) Freeway.

The unidentified officer was one of several who responded to reports of what neighbors thought were fireworks shortly after noon, said Long Beach police Sgt. Rico Fernandez.

The Contra Costa Times reports that as they searched an alley near Bort Street and Butler Avenue, a dry-ice bomb hidden inside a plastic bag exploded, sending the officer reeling.

Fernandez described the officer’s injuries as minor.

A third, similar explosive was discovered at the other end of the alley, which runs behind homes and apartments in a neighborhood just south of the 91 Freeway, Fernandez said.

The Los Angeles County Sheriff’s Department Bomb Squad was called in to detonate the third device, and residents were temporarily evacuated to avoid further injuries.

A dry ice bomb is a homemade device that uses water, a bottle and dry ice, or frozen carbon dioxide.

It can take anywhere from thirty seconds to an hour for a dry-ice bomb to rupture, depending on temperatures outside of the bottle, according to California criminal codes banning the devices.

Officers are investigating who planted the bombs and why. No arrests had been announced as of Sunday afternoon.

The Times notes that the latest incident is not the first time Long Beach or surrounding cities have seen multiple dry-ice bomb explosions in a single day. In the 1990s, a spate of similar explosions in Norwalk forced authorities to issue public warnings about the dangers linked to these explosives, which often cause serious injuries to both unsuspecting victims and bomb-makers.