SAN DIEGO (CNS) - A couple dropped off an 81 mm mortar at a California Highway Patrol office in the Morena area Tuesday, prompting a bomb squad rollout and evacuation.

The couple who arrived at the CHP station on Pacific Highway about 8:15 a.m., telling officers they found the mortar while cleaning out a vacant home in Clairemont, according to the San Diego Fire-Rescue Department.

Taking no chances, authorities cleared the building and closed a section of the highway, while waiting for a bomb squad to determine if it was explosive, fire department spokesman Maurice Luque said.

Luque said the mortar contained explosives but lacked a complete fuse system, rendering it essentially harmless. The bomb squad impounded the device and gave an all-clear about 9:45 a.m., Luque said.

Anyone who finds old ordnance that they believe could be explosive should call 911.

"Don't touch it; don't drive it to a fire station or a police station," Luque said. "Leave it where it is, call 911, and let us handle it."

The origin of the mortar was unclear.