FRESNO COUNTY, Calif. (KSEE/KGPE) – Multiple people were injured after a circuit breaker explosion inside the Eastwood Power Station Tunnel in the Shaver Lake area of Fresno County, according to the Fresno County Sheriff’s Office.

Cal Fire crews say they responded to an incident Thursday afternoon – with smoke reported in an underground vault. The sheriff’s office adds that Southern California Edison employees were working in the area and exposed to smoke and gasses. Eight workers were evaluated for possible exposure.

The incident is in the area of the Sierra Marina parking lot.

In a statement, Southern California Edison officials say electric service to customers was not been affected by this outage.

At this time, it is still unclear what caused the outage and we have mobilized a team to assess the impact and work toward restoring power generation once it is deemed safe to do so. We also requested Cal Fire’s assistance as a precaution. We are making all necessary resources available to facilitate the safe restoration of our Eastwood Powerhouse operations, while ensuring the safety and security of the public.

Gabriela Ornelas, Southern California Edison

Officials add that there are no external power issues or threats and there is no active fire.