An underground utility vault exploded just after 9:40 a.m. Friday several blocks away from Union Square, according to police who have blocked off the area.
Pacific Gas and Electric crews were called to the intersection of Mason and Cyril Magnin streets and are inspecting the underground vault, which they accessed from manholes.
PG&E spokesperson Jennifer Robison said the incident did not cause any outages in the area and they are investigating what caused the problem.
Robison said a vault is an underground facility through which a small number of customers are served.
San Francisco Police Sgt. Frank Fagan said the police are redirecting traffic in the area in case a manhole is blow off.
“These manholes covers are very heavy. If they go they could blow off,” said Fagan.
PG&E has been in hot water recently after a substation fire caused power loss across much of San Francisco on April 21.
The company has said it will inspect its 46 substations in San Francisco. It is unclear if the explosion Friday was at a substation on another type of facility.