A 20-metre crane has collapsed on a cluster of properties in east London, killing one person and injuring four others.
Crews battled to free those stuck in two terraced houses and a block of flats under construction on Compton Close which were crushed in the accident.
A woman was found on the first floor of one of the houses and confirmed dead at the scene.
A video posted online by a witness showed the top storey of the four-floor block of flats caved in with the crane lying on top of it.
Mayor of London Sadiq Khan tweeted: "This is a tragedy. My heartfelt condolences go out to the family of the victim who died during this incident in Bow today. I sincerely hope that the four individuals injured make a full recovery."
A London Ambulance Service spokesperson said: "We were called at 2.42pm to reports of an incident involving a crane collapsing near Watts Grove, Bow.
“We dispatched a number of specialist resources including an advanced paramedic, ambulance crews and our hazardous area response team (HART), with the first of our medics arriving within three minutes.
"We treated four people at the scene. We treated two of these patients for head injuries and took them to hospital and we assessed the other two patients at the scene.
"Sadly, despite the efforts of emergency services, a fifth person was found and died at the scene."
Basil Long, a 39-year-old housing lawyer, lives opposite the construction site where the crane came down.
"It was a real shock when I saw it fall," he said. "I had actually been in the bedroom at the time. There was a lot of shouting going on.
"I literally saw it topple over. It was terrifying. You could see the people in the tower trying to run down as fast as they could. I'm still shaking."
National officer of the Unite union, Jerry Swain, said there must be "an urgent, full and complete investigation into the circumstances that led to this accident".
He added: "The preliminary findings of which must be released in weeks, rather than months or years, in order to ensure that similar accidents are avoided in the future."
The crane that collapsed was being used by Swan Housing Association and NU living.
A spokeswoman for Swan Housing Association and NU living said: "Swan Housing Association/NU living is aware of an incident that occurred at our Watts Grove development site in Tower Hamlets, east London, this afternoon.
"A full incident response has been implemented and our staff are on site supporting the emergency services in their response."
