LONDON (AP) -- Britain's Heathrow Airport will be closed Friday after a fire at an electrical substation knocked out power to the airport and thousands of homes.

About 150 people had to be evacuated after a transformer within an electrical substation caught fire in west London.

"To maintain the safety of our passengers and colleagues, we have no choice but to close Heathrow" for the full day Friday, the airport's statement said. "We expect significant disruption over the coming days, and passengers should not travel to the airport under any circumstances until the airport reopens."

It said it will provide an update on its operations when it has more information on restoring power available.

London Fire Brigade said 10 fire engines and around 70 firefighters were on the scene.

"The fire has caused a power outage affecting a large number of homes and local businesses, and we are working closely with our partners to minimize disruption," Assistant Commissioner Pat Goulbourne said.

Footage posted to social media showed huge flames and large plumes of smoke coming from the facility.

Scottish and Southern Electricity Networks said in a post on X the power outage affected more than 16,300 homes.

Emergency services were called to the scene at 11.23 p.m. Thursday. The cause of the fire is yet to be determined.

Goulbourne urged people to take safety precautions and avoid the area as crews worked to extinguish the blaze.

Heathrow is one of the world's busiest airports for international travel. The U.K. government earlier this year approved building a third runway at the airport to boost the economy and connectivity to the world.