One person has died and a major search operation is under way for three others after a building collapsed at a power station.
Five people are being treated in hospital after the iron and steel structure at the derelict Didcot A site in south Oxfordshire came down while it was being prepared for demolition.
A further 50 people were treated for dust inhalation at the scene, where a "major incident" was declared shortly after emergency services were called at 4pm.
Oxfordshire deputy chief fire officer Nathan Travis said specialist urban search and rescue teams, including sniffer dogs, are at the "challenging" site from as far away as the West Midlands.
He said: "The building is potentially 10 storeys high, half of that building has collapsed, so you have got a rubble pile which is approximately 20 to 30 feet deep at the moment.
"The search will be considerable due to the instability of the site, we expect the search to continue throughout the night and possibly into the coming days."
Asked what the chances were of finding the missing alive he replied: "At the moment I can't give you any details on that but it is a substantial collapse of a building."