An assault rifle was stolen from an unmarked San Francisco police car over the weekend, police said Sunday.

The car was parked and locked while officers worked in the area when unknown suspects broke in and stole the AR-15 rifle, Sgt. Michael Andraychak said Sunday.

The AR-15 is a type of rifle issued to specially trained officers so that they are available for rapid deployment during incidents such as a barricaded suspect, Andraychak said.

The department has issued a teletype to alert law enforcement agencies, and an investigation is underway.

Andraychak said that "no resource is being spared to recover this weapon."

Anyone with information is asked to call police at (415) 553-1373 or the anonymous tip line at (415) 575-4444, or text a tip to TIP411 and start the message with SFPD.