A resident has died in a fire which broke out at a home for people with learning disabilities.
The huge blaze started in Connington Crescent, Chingford, north-east London, at 02:14 BST and was out by 05:24.
Eight residents and four carers managed to get out of the three-storey building before firefighters arrived.
Iain Duncan Smith, MP for Chingford, said a neighbour called 999 because residents "didn't know what the number was".
When the ten fire crews arrived, two floors and the roof of the building were alight, London Fire Brigade (LFB) said.
The body of the woman, who lived in "supported living flats" at Connington Court, was found inside the building.
Sequence Care Group, which runs the home, said "further checks will be carried out" across all of its services.
A further 16 people were evacuated from neighbouring properties before firefighters arrived.
Mr Duncan Smith described the death as a "terrible tragedy", and said "it could have been worse" had a neighbour not alerted the emergency services.
He said the woman "saw all the smoke coming out and saw them all running around the place".
"She asked has anyone called the fire brigade and they said no because they didn't know what the number was," he added.
"The fire brigade were here very quickly and thanks to the neighbour they were called, and the ambulances too, so great credit to the neighbour."
At its height, 72 firefighters - from Woodford, Chingford, Walthamstow, Enfield and Leytonstone fire stations - were sent to tackle the blaze.
Richard Janssens, station manager for Chigwell, said care home staff were "desperately trying to evacuate the building".
He added: "The initial  call did come from a neighbour."
Mr Janssens said specialist fire investigators in the building "are working in close liaisons with the police officers to find out what the cause of the blaze is and what the circumstances were which led to this tragic fatality".
At the scene: Greg McKenzie, BBC Radio London
When I arrived at Connington Crescent there were a lot of fire engines and police officers in the area - and I could see eight residents standing outside before they were taken away.
The smell of smouldering smoke still lingered in the area until about 07:00.
As the morning got lighter, you could see the damaged roof of the care home which is completely gutted.
Staff I have seen are visibly shaken and upset, while nearby residents have told me about how shocked they are with the fatality.
LFB station manager Keith Williams said firefighters "have been working hard to contain the spread of the fire which has destroyed the roof".
"Crews expect to be here into the day, tackling hot spots," he added.
The Met Police said "a number of people" have been treated for smoke inhalation, and that officers remain at the scene.
One local resident, who works at another care home, said: "It is a big concern because you do worry about your actual residents more than you do for yourself and try to get them out.
"So it is extremely sad news that someone has actually died."
The building contains two supported living services, Connington Court and Connington House.
The Care Quality Commission (CQC) said the two homes, both run by Sequence Care Group, catered for "adults with learning disabilities who may also have autism, complex needs or behaviours that challenge services".
Greatly saddened by the horrific fire at a Chingford care home in which a resident died. My thoughts are with the victim's family. I have been in touch with my Deputy Mayor for Fire and the Commissioner this morning. My thanks to the firefighters who tackled the blaze.— Mayor of London (@MayorofLondon) April 20, 2018
Sequence Care Group said it was "shocked" by the death of the resident.
A spokesman added: "The safety and well-being of our residents is always our main concern and while we believe that the processes that we have in place to ensure fire safety are robust, in the light of last night's events we are carrying out further checks across all of our services.
"We are working closely with the emergency services to establish exactly what happened to cause the fire. It would be inappropriate to make any further comment at this stage."
Connington House was previously inspected by the CQC in December 2017 where it was given a "good" rating. Connington Court currently has the same rating following its last inspection in September 2016.