San Francisco police and firefighters responded to a report of an explosion involving a FedEx truck in the city's South of Market neighborhood this afternoon but didn't find any damage.



There was also no one injured in the incident, which was reported at 2:01 p.m. near Sixth and Tehama streets, fire department spokeswoman Mindy Talmadge said.



Police spokeswoman Officer Tracy Turner said the FedEx driver called 911 to report an explosion.



When officers arrived, however, they could not find any sign that an explosion had occurred, Turner said.



A bomb squad responded and Tehama and Sixth streets were shut down, but the streets reopened about an hour later.



The FedEx truck appeared to be intact, and the driver declined to speak with reporters at the scene.



Turner said it is possible that someone threw a firecracker in the area of the truck.



Michael McKinney, a security guard who works on that block of Tehama Street, said there was a similar incident on Monday involving a report of an explosion with no damage.



He said he heard a loud bang that day, and wondered if someone had thrown some sort of explosive object from a window.



Talmadge said initial reports indicated that the explosion might have been caused by a package in the truck containing fireworks, but Turner said police determined that was not the case.