An underground electrical fire caused a brief power outage in Downtown Saturday night and interrupted bus and train service for about 30 minutes, according to the Long Beach Fire Department.

The fire broke out around 10 p.m. in an underground electrical vault on Pine Avenue between Ocean Boulevard and First Street, Long Beach Fire Department spokesman Capt. Jack Crabtree said.

Southern California Edison arrived on the scene quickly to cut power to the vault so electrical and fire crews could confirm the flames hadn’t spread. Once power is cut, these vault fires usually extinguish themselves, Crabtree said.

Power and transit operations were both restored by about 10:30 p.m., Crabtree said.

The cause of the fire was not immediately clear, but similar incidents often occur when a vault is overloaded, according to Crabtree. Long Beach, like much of California, is in the middle of a heat wave that may be putting extra strain on the electrical grid.

Southbound Pine Avenue remains closed to traffic as Edison continues to assess the damage. A worker on site said the closure would likely last for several hours.

Brandon Richardson is a reporter and photojournalist for the Long Beach Post and Long Beach Business Journal.