Heathrow airport partially reopened Friday afternoon after massive fire in west London resulted in a power outage overnight that cause global travel delay.

"Our teams have worked tirelessly since the incident to ensure a speedy recovery," the airport wrote on the social media platform, X. "We’re now safely able to restart flights, prioritising repatriation and relocation of aircraft."

Airport officials informed travelers not to go to the airport unless advised to by their airline and said they hope Heathrow will be fully operational by Saturday.

The fire started in a transformer in an electrical substation in the town of Hayes, in west London. At least 10 fire engines and about 70 firefighters have responded to the blaze, the London Fire Brigade said.

The cause of the fire has yet to be identified.

Hundreds of flights have been canceled or rerouted due to the incident and multiple people had to be evacuated from the airport.

The Metropolitan Police in London said it had counterterrorism specialists leading the investigation, according to The New York Times.