Businesses and residents in northern California are being urged by the state's power grid operator to conserve energy because of heavy damage to transformers following reports of gunshots.

The California Independent System Operator asked those near San Jose, Santa Clara and Silicon Valley to reduce their energy use after the apparent vandalism of the Metcalf transmission substation. Gunshots were reported in the area early Tuesday morning, but Santa Clara County Sheriff's Detective Kurtis Stenderup told NBCBayArea.com it is too early to tell if the gunshots are related to the damage.

The vandalism caused about 10,000 gallons of oil to leak from the transformers. Hazardous material crews were cleaning up the mess.

Two hours after the gunfire was heard, PG&E Corp's Pacific Gas and Electric reported to the authorities that the security fence protecting the equipment had been breached.

At least five transformers were damaged.

"As damage assessments continue, additional equipment at the substation may be taken out-of-service. This will limit transmission capability in this area of the high-voltage grid, which is why conservation is required," California ISO said in a release.

Consumers were asked to reduce energy use until midnight. Hours after the incident, there were no reports of customers without power, according to Pacific Gas and Electric.