SAN DIEGO - A customer brought an object resembling a pipe bomb to a Kearny Mesa car lot Wednesday, prompting an evacuation of the business until authorities determined that the tube was a homemade marijuana container.

The patron found the roughly 6-inch-long plastic cylinder in the street about 8:30 a.m. while on the way to the Mercedes-Benz dealership in the 4700 block of Kearny Mesa Road, according to the San Diego Fire-Rescue Department.

He carried it onto the grounds of the auto business and showed it to mechanics, who decided to make an emergency call because they thought the object, which had caps on both ends, might be a makeshift explosive device, SDFRD spokesman Maurice Luque said.

Everyone at the business -- about 300 people -- evacuated while a bomb squad was en route to investigate.

The explosives team used a remote-controlled robot to blow the pipe open about 10:15 a.m., finding a stash of cannabis inside, Luque said. The dealership was then cleared to reopen.

The cylinder apparently had been attached to the underside of a vehicle before falling off near the intersection of Convoy and Daggett streets, the spokesman said.