A woman is in a critical condition after being hit by a pile of bricks which appear to have fallen from a crane in Mile End, east London.
The Met Police said the 28-year-old woman was "injured by falling debris" on Burdett Road at 09:38 BST.
She was taken to a major trauma centre in east London, according to the London Ambulance Service (LAS).
The Health and Safety Executive said it was aware and was investigating the incident.
Eyewitness Alan Harris told the BBC he alerted the emergency services after "hearing a loud crash and a woman screaming for an ambulance".
Footage posted on social media showed bystanders, paramedics and police officers rush to treat the injured woman.
Bricks and debris can be seen scattered around the woman as she lay on the pavement.
Police say the woman's next of kin have been informed.
A second person, a man, was also taken to hospital to be treated for shock, according to the Met Police.
Buses were diverted away from the scene, with Burdett Road being closed between St Paul's Way and Agnes Street.
LAS said it dispatched multiple ambulance crews to the scene and London's Air Ambulance also sent a crew to Burdett Road's junction with St Paul's Way.
The crane, from which the bricks are believed to have fallen, is perched on a development site called Bow Corner.
Steve Boreham, construction director of Higgins Homes which is responsible for the scheme, said the company's "priority" was to "make the area safe".
He added: "Our primary thoughts and concerns are with the lady who has been injured and those affected today.
"We are working with the Health and Safety Executive who are investigating the incident to determine the cause and will release more information as soon as it is available."
Planning permission was granted by Tower Hamlets Council in March 2016 to demolish the existing buildings and begin work to build 19 new homes.