British energy watchdog Ofgem has launched an investigation after a report found a fire that caused the shutdown of Heathrow Airport was due to a preventable technical fault.

Heathrow Airport said it is “open and fully operational” on Saturday after the airport was shut over a loss of power caused by a substation fire.

Flights have begun landing at Heathrow as it aims to return to normal operation on Saturday after the airport was shut over a loss of power, with restrictions on overnight flights temporarily lifted.

More than 200,000 air passengers have had their flights to or from Heathrow cancelled after the airport was forced to close on Friday after a blaze broke out at a nearby electrical substation