BC Hydro has restored power to all 50,000 customers after fire at a substation in Chilliwack caused outages across the Fraser Valley Friday.

Fire crews extinguished the fire shortly after noon at the Atchelitz Substation near the intersection of Lickman and South Sumas roads.

The fire broke out shortly after 9 a.m. and fire crews had remained on site over concerns the oil from the transformer's storage tank could reignite.

The tank holding approximately 115,000 litres of insulating oil had caused an explosion and an intensive cleanup is underway.

BC Hydro said the cause of the fire is still under investigation and spill response teams are assessing environmental damage.

Chris Brumwell, BC Hydro spokesman, said 12 employees were inside the facility at the time of the accident but all have been accounted for and confirmed safe.

"A few have gone to hospital just for precautionary reasons," Brumwell added.

Officials are still warning neighbouring residents to stay indoors, close windows and doors and turn off furnaces for safety.

The Twin Rinks and Cheam Centre recreational facilities, as well as the Chilliwack Library have been closed due to power outages.

The following schools have also been closed for an early weekend: Sardis Elementary, Vedder Elementary, Vedder Middle, CHANCE Alternate School, Tyson Elementary, Unsworth Elementary, Yarrow Elementary, Evans Elementary, Cultus Lake Elementary, Watson Elementary and Shxwetetilthet.