Three workers were seriously injured this afternoon when scaffolding on a partially built building collapsed, hospital officials and police said.
Eyewitnesses said the scaffolding on the building in Milton Keynes, north of London, fell like a "pack of cards".
Thames Valley police said three people had been rescued from the site and taken to hospital.
"We have received three casualties," a spokesman for Milton Keynes General Hospital said. "All are classed as being seriously injured."
"We have not received any fatalities or any minor injuries." Chief Inspector Andy Standen of Thames Valley police said all other workers were thought to have been accounted for. Standen said firefighters had been using heat-seeking equipment to recover people trapped on the site at a new Jury's Inn hotel development at Witan Gate.
"We don't think there is anybody outstanding," Standen told reporters. "The building contractors themselves have done a roll call."
One witness reported a "huge roar" as debris plunged to the ground. "I saw it concertina down," witness Doug Masson told reporters. "It took no more than 20 seconds to fall. "It sounded like a low rumbling of thunder."
Television footage showed debris strewn across a large area. Local resident Christopher Key told Sky News the collapsed scaffolding looked like a "pile of matchsticks". Up to 20 ambulances and two air ambulances were called to the scene.