ANTIOCH (CBS SF) – Two firefighters suffered an electrical shock from an illegal power bypass while battling a late night two-alarm house fire in Antioch, authorities said.

Contra Costa County Fire Capt. George Laing said two residents of the home also received medical treatment for minor burns suffered as they were trying to escape the flames.

The blaze was reported at 10:47 p.m. in the kitchen of at a house in the 3500 block of Blythe Drive.

“The first units (on the scene) saw heavy smoke and flames coming from the back corner and called in a second alarm,” Laing said.

As the firefighters were extinguishing the kitchen fire, two of them received a strong electrical shock.

“Securing the utilities, as they were fighting the fire, two of our firefighters were injured and shocked by electrical current which came from a bypass which is a way of stealing power before it gets to the meter,” Laing said. “It’s unprotected.”

He said fortunately the firefighters were not seriously injured and have returned to duty.

Lang said investigators were trying to determine if the occupants of the home — who were renters — were responsible for the illegal bypass or if the home owner install it.

“The fire is still under investigation, in part to determine who modified the electrical system,” Laing said.”There are potential criminal charges pending due to the theft of power and the injury to firefighters.”

The fire was brought under control at about 11:30 p.m. A cause has yet to be determined.