Air passengers from  across Hertfordshire have been told they "should not travel"  to Heathrow Airport under "any circumstances" today after it was forced to close following a major fire  at a nearby electrical substation.

More than 1,300 flights to and from the airport will be disrupted today and thousands of homes have been left without power and more than 100 people were evacuated after a transformer within the North Hyde electrical substation caught fire in west London.

The airport, which is supplied by the substation, said it was among those impacted by the power outage.

Online flight tracking service FlightRadar24 said the closure would affect at least 1,351 flights to and from Heathrow.

It said 120 flights to the airport were in the air when the closure was announced.

Heathrow is the UK’s largest airport, with more than 83.9 million passengers travelling through its terminals in 2024.

A Heathrow spokesperson 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.

“To maintain the safety of our passengers and colleagues, we have no choice but to close Heathrow until 23h59 on 21 March 2025. We expect significant disruption over the coming days and passengers should not travel to the airport under any circumstances until the airport reopens.

“We will provide an update when more information on the resumption of operations is available. 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.”

Online tracking services showed flights being diverted to Gatwick, Charles de Gaulle Airport in Paris and Ireland’s Shannon Airport.

Scottish and Southern Electricity Networks said on X there was a large-scale power outage in Hayes, Hounslow and the surrounding areas impacting more than 16,300 homes.

A National Grid spokesperson said the fire had damaged equipment and they “working at speed to restore power supplies as quickly as possible”.

London Fire Brigade said 10 fire engines and around 70 firefighters were on the scene at Nestles Avenue in Hayes.

Around 150 people have been evacuated from surrounding properties and a 200-metre cordon has been put in place as a precaution.

Assistant commissioner Pat Goulbourne said: “This is a highly visible and significant incident, and our firefighters are working tirelessly in challenging conditions to bring the fire under control as swiftly as possible.

“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 minimise disruption.”

Firefighters led 29 people from surrounding properties to safety.

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

The brigade said nearly 200 calls had been received in relation to the incident with crews from Hayes, Heathrow, Hillingdon, Southall and surrounding areas on the scene.

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

Mr Goulbourne said firefighters urged people to take safety precautions as crews worked to extinguish the blaze.

“This will be a prolonged incident, with crews remaining on scene throughout the night,” he said.

“As we head into the morning, disruption is expected to increase, and we urge people to avoid the area wherever possible.”

London Ambulance Service and Metropolitan Police both confirmed they were on scene supporting fire crews.