A man has been arrested on suspicion of murder after three children and a woman died in a house fire in north-west London.

The children – a girl, 15, and two boys, aged eight and four – and the woman, 43, were killed in the fire in the Stonebridge area of Brent.

A 41-year-old man was arrested at the scene on suspicion of murder and remained in custody, the Met police said.

Officers were called at 1.22am to help the London fire brigade, who were tackling the blaze.

Eight fire engines and about 70 firefighters were sent to the site, the LFB said. Firefighters said the woman and one of the children were rescued from the second floor of the house but were declared dead by air ambulance crews.

The other two children were found inside the property as crews were tackling the fire, and were also declared dead at the scene, the LFB said.

The fire was brought under control by about 3.25am. The next of kin of the four people had been informed, the police said.

Two other people, a woman in her 70s and a teenage girl, were taken to hospital by the London ambulance service.

Supt Steve Allen, from the Met’s local policing team in north-west London, said: “This is an extremely tragic incident and our thoughts are with everyone involved. Officers arrested a man at the scene and we continue to work alongside investigators from the London fire brigade to establish the cause of the fire.”

Emergency services would remain in the area throughout Saturday, he said.

Mohamed Labidi, a 38-year-old teacher who lives nearby, told the PA Media news agency that he “can’t even look at the house”. He said he knew the woman and called the four who died in the fire “really good people”.

“We used to socialise together. I can’t even look at the house right now,” he said.

A person who lives next door to the house but did not wish to be named, said: “It’s horrible, we saw people running outside. It’s hard to process. I only just moved in so it’s hard to think about it.”

Dawn Butler, the Labour MP for Brent East, said in a post on X that she was “devastated” to see the fatal fire. “My prayers are with the family and friends affected by this very sad tragedy. LFB-Brent worked hard to get it under control, thank you.”

The LFB assistant commissioner Keeley Foster said: “This is an extremely tragic incident, and the thoughts of everyone across the brigade are with those impacted by this incident.

“Our specialist fire investigation unit are working closely with colleagues from the Metropolitan police service to now determine the cause of this fire. We are working closely with our partners to support the community at this very sad time.”