Officials say they first got a report of a car explosion around 2:01 p.m. The driver told a 911 dispatcher he was driving east when he heard a loud explosion at the rear of the truck.
When the bomb squad arrived they found signs of an explosion on the vehicle, but did not find any explosives nearby.
No injuries were reported but roads nearby were shut down and Muni lines were diverted as police investigated. Roads reopened a short time later.
(Stay with ABC7 News for the latest on this developing story.)