A huge fire has broken out at an electrical substation in west London.
Around 100 firefighters, drawn from crews based at Paddington, Euston and surrounding fire stations, were tackling the blaze on Aberdeen Place in Maida Vale, where an electrical transformer was alight.
That part of the blaze "is now under control," London Fire Brigade (LFB) said, but warned "firefighters are continuing to work to fully extinguish it".
The roof and a flat of a neighbouring residential building were also alight, but this fire has been brought under control, too, LFB said.
"Around 100 residents [including elderly and vulnerable people] were evacuated from their homes, but some have now returned," LFB assistant commissioner Pat Goulbourne said.
Steve Pennington, from Westminster City Council's Welfare Response Team, said teams were helping those affected.
"We have got residents that have been displaced and we are trying to help them as best we can," he said outside the Wharncliffe Gardens Community Centre.
"We have had a number of residents, some of them elderly, some of them requiring assistance from the local authorities."
A major incident, which was declared just before 8.30am, was stood down around 11am, Mr Goulbourne said.
There have been no reports of any injuries at this time, the brigade said.
Firefighters will continue to work "for some time on the transformer at the substation," Mr Goulbourne said, where crews "have been deploying foam to suppress the flames" of what he described as a "technically complex fire".
LFB has deployed a 32-metre turntable ladder "to tackle the fire from above," he said, while drones are providing commanders with "a greater situational awareness of the incident".
Pictures from the surrounding areas show thick black smoke blowing across the city's skyline.
The brigade said its scientific advisers were monitoring air quality in the local area as crews responded.
LFB said it received more than 170 calls about the blaze from around 5.30am on Tuesday and sent 15 fire engines.
"This is a very visible fire, which is producing lots of smoke," said station commander Paul Morgan.
"Residents are advised to keep their windows and doors shut and avoid the area where possible."
UK Power Networks said the blaze was caused by faulty equipment in the substation.
It added that the fire had not interrupted the power supply to the area and "customers' supplies were not impacted".
It comes a month after Heathrow was shut down following a fire at a nearby electrical substation.
The Metropolitan Police said it was not treating that fire as a criminal matter after more than 1,000 flights were cancelled and hundreds of thousands of passengers affected.
Fatima Bazzi, 71, who lives next to the substation, said: "I wake up, I smell something wrong, I go to my sitting room and I see smoke."
Her daughter Alice, 36, said it was sad "that any flat, any of my neighbours have to lose any of their belongings of a fault that's not their own".
Marc Whitehouse, 44, who was staying with his girlfriend Adele Dillon at a flat in Aberdeen Place, said: "Some of the bangs sounded like scaffold planks being thrown away. I woke up at six o'clock and thought 'Who's starting work at this time in the morning?'
"And she (Ms Dillon) came in and said 'the substation is on fire'."
Ms Dillon, 54, who uses a wheelchair, said it was "popping and crackling" when she opened the curtains at 6am.
The couple left the flat, taking their dog and two cats with them, and were among a dozen people waiting at a nearby community centre for updates.
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Shirin Valipour, a resident who lives near the substation, said she noticed a black cloud at around 6.15am but saw "no flames".
"It then built up rapidly with raging flames by 7.30am," she added. "At that time we were thinking of actually leaving, they managed to bring it under control by 8.30am and we're so grateful to the brave firemen who were in the middle of the smoke."
