LONDON - The first plane landed at London Heathrow on Friday as the airport resumes some flights following its closure caused by a major fire at an electrical substation nearby.

"Following an earlier power outage, Heathrow is now safely able to restart flights," the airport said in a statement.

"To maintain the safety of our passengers and colleagues, Heathrow will be running a reduced operation prioritizing repatriation and relocation of aircraft," it said, while suggesting passengers contact their airline for further information.

To help ease congestion following the closure of the airport, restrictions on overnight flights have been temporarily lifted, the Department for Transport said in a post on X.

Heathrow, one of the world's busiest airports, hopes to run a full service on Saturday. The closure is estimated to have disrupted the travel plans of 200,000 people, The Guardian reported.

The airport's chief executive Thomas Woldbye apologized on Friday to passengers, calling the incident "as big as it gets for our airport." "Tomorrow morning we expect to be back in full operation, so 100 percent operation as a normal day," Woldbye said.

Meanwhile, counter-terror officers from the Metropolitan Police are leading the investigation into the fire at the nearby electricity substation that has closed the airport.

A Met spokesperson said its Counter Terrorism Command was leading the investigation due to "the location of the substation and the impact this incident has had on critical national infrastructure."

There was "currently no indication of foul play," but the spokesperson added that officers were retaining an "open mind at this time" regarding the cause of the blaze.

Flights had been canceled, people evacuated from their homes, and local schools shut after two explosions and a fire at an electrical substation in Hayes, west London, on Thursday night. Some planes had been diverted to other airports, including London Gatwick Airport, those in Paris, and Shannon Airport in Ireland.

The airport, which handled a record 83.9 million passengers last year, said its backup diesel generators had "all operated as expected... but they are not designed to allow us to run a full operation."

Ofgem, Britain's energy regulator, announced it would commission a review "to understand the cause of this incident and what lessons can be learned".