A fire at an electrical substation in west London, which supplies Heathrow, caused a major power outage at the airport, prompting its closure.
It is not yet known what caused the fire at the substation, but Transport Secretary Heidi Alexander said there was no suggestion of foul play as counter-terrorism police investigate.
“The counter-terrorism command has specific capabilities and capacities that mean that they are used to conducting investigations at pace,” she said, adding that they were needed as the fire took place next to a critical piece of national infrastructure.
Emergency services were first called to Nestles Avenues in Hayes, west London at 23:23 GMT on Thursday.
Jonathan Smith, London Fire Brigade (LFB) deputy commissioner, said the fire at the electrical substation involved a transformer containing 25,000 litres of cooling oil.
The fire was “very visible and significant,” he said. The LFB said the fire was under control by 06:28.
On Friday evening, the service said the fire was “believed to be non-suspicious” and the investigation will “focus on the electrical distribution equipment”.
Commander Simon Messinger, who is leading the Metropolitan Police’s response to the fire, said: “Various specialist investigators continue to examine the scene and it is expected to take some time before full assessments can be completed.”
But he repeated that “at this stage, there remains no indication of any foul play”.
The substation is about a mile and a half away from the airport.
Energy Secretary Ed Miliband told BBC Radio 4’s Today programme the substation’s back-up generator “appears to have been knocked out”.
Videos shared on social media showed tall flames and plumes of smoke billowing from the substation overnight.
People living nearby were advised to keep doors and windows closed to avoid smoke inhalation.
