Health concerns have been raised following a fire at a BC Hydro substation near Chilliwack, east of Vancouver, that left 38,000 customers in the region without power on Friday.

Residents in the area were advised to close their doors and windows while officials try to determine whether the smoke posed a health risk.

"To ensure your safety, Chilliwack’s Emergency Operations Co-ordinator is advising residents to stay inside your current shelter if safe to do so, close your windows and turn off your furnace," a statement issued by BC Hydro at 11:20 a.m PT. said.

The fire broke out about 9:30 a.m. PT when unconfirmed reports suggest some leaking fuel caught fire at the Atchelitz substation, located on a farm land just west of Chilliwack near the intersection of Lickman Road and South Sumas Road.

Atchelitz substation

The flames spread to a nearby transformer, which exploded as it burned out of control. Thick black smoke could be seen rising hundreds of metres into the air.

By noon, fire crews managed to get the flames under control.

"Employees that were in the substation have been accounted for and confirmed safe. One person has been transported to hospital as a precautionary measure," BC Hydro said in a statement issued at noon.

Cause unconfirmed

The official cause of the fire remains unconfirmed, the statement said, adding a spill response team was en route and an environmental assessment team will be investigating.

While the fire burned BC Hydro turned off at the Atchelitz substation for the safety of fire crews at the site, leaving thousands in Chilliwack, Sumas, Atchelitz and Abbotsford without power.

Smoke from a fire at a Chilliwack substation could be seen several kilometres away on Friday morning. (Renee Filippone/CBC)

By noon power had been restored to some customers in the Chilliwack area, but as many as 27,000 in Atchelitz and Sumas remained without power.

The Atchelitz substation serves approximately 50,000 customers.