Flames engulfed an Ocean Beach home Thursday afternoon, prompting evacuations as loud popping sounds caused by discharging ammunition sounded from within the burning home. The blaze in the 4400 block of Niagara Avenue erupted for unknown reasons shortly before 2 p.m., the San Diego Fire-Rescue Department reported. Patrol officers cleared people out of nearby residences as firefighters were en route. An SDFD chief confirmed that dozens of rounds of ammo went off when the garage of the house was burning. It took firefighters about 15 minutes to subdue the blaze, according to SDFRD public affairs. There were no immediate reports of injuries. The cause of the fire was under investigation.