London’s Heathrow Airport closed on Friday after a fire at a nearby electrical substation caused a power outage, airport officials said.

“Heathrow is experiencing a significant power outage across the airport due to a large fire at a nearby electrical substation. Whilst fire crews are responding to the incident, we do not have clarity on when power may be reliably restored,” a Heathrow spokesperson said.

“We expect significant disruption over the coming days and passengers should not travel to the airport under any circumstances until the airport reopens,” the spokesperson said.

The airport will remain closed until at least 11:59 p.m. local time on Friday.

“We know this will be disappointing for passengers and we want to reassure that we are working as hard as possible to resolve the situation,” the spokesperson said.

The closure of Europe’s busiest airport disrupted more than 100 flights that were in the air and forced to divert or return to their originating airports, according to flight-tracking site Flightradar24.

Some 145,000 passengers could be affected by the closure, according to aviation-data firm Cirium.

Heathrow Airport has an estimated 1,300 take-offs and landings at the airport per day, according to its website. Heathrow handled a record 83.9 million passengers last year — a nearly 6% increase from 2023.

Airport officials said they will update travelers “when more information on the resumption of operations is available.” Travelers can check Heathrow Airport’s website or social media platforms, including X.

– CNBC’s Leslie Joseph’s contributed to this report.