At least one person is said to have died and several more left injured by a major explosion at a power station in England that caused part of it to collapse.
Witnesses said Didcot Power Station in Oxfordshire was felt "shuddering" after the blast, while others described it collapsing "in a huge pile of dust".
Six ambulances and two air ambulances have been sent by South Central Ambulance Service, which said the explosion was a "major incident".
It is not yet clear whether the blast at about 4pm today was planned, with demolition of the site expected to be completed by the end of the year.
Rodney Rose, deputy leader of Oxfordshire County Council, said: 'I have been told there has been one fatality, but the rest is currently unknown.
'The fire service is there now and we are still trying to find out if this was a demolition.'
Mr Rose told the Oxford Mail: "At the moment this is being treated as a collapsed building, not an explosion, but there was a bang."
Thames Valley Police confirmed its officers are at the scene while a South Central Ambulance Service spokesman said there were several casualties.
Shocked witnesses have described an "explosion" and "loads of dust" and told of a heavy emergency services presence.
Bill McKinnon, who said he lives about 400 yards away from the site, told the BBC: "I heard the explosion and the very loud rumbling.
"By the time I had got up and looked out of the window there was a huge cloud of dust which came through and over our village.
"When that had cleared I noticed that half of the old power station, where they used to keep the generators, half of that was missing.
"There wasn't any physical feeling, it was only noise. When they took down the cooling towers a couple of years ago it was about the same volume as that. It was quite loud."
He added: "I was a little bit surprised because normally the contractors let us know when they are going to do explosions, so I was a bit surprised because we hadn't heard anything.
"Very shortly afterwards the air ambulance turned up and then fire engines and ambulances started arriving, and a little while after that another air ambulance turned up, and I think they are still there."
Mr McKinnon said the explosion took place in a large building which housed the generators for producing power.
Pictures from the scene showed a significant chunk of a building in the defunct Didcot A site has collapsed, with a large amount of debris on the ground.
David Cooke, whose company Thames Cryogenics have a building overlooking the power station, also saw the incident unfold.
He said: "Our building shook and as we looked out of the window, the end of the main turbine hall collapsed in a huge pile of dust.
"It totally obscured the towers and must have drifted across the roads and main rail line. What's left looks a tangled mess.
"The dust was hanging over the area for five to ten minutes. First thought was, it didn't looked planned, followed by the thought that people are going to have been hurt."
Ed Vaizey, Conservative MP for Didcot and Wantage, tweeted: "Very concerned about terrible events at Didcot power station. Praying for workers and their families."
He told BBC News: "There is a coal power station there and there is a gas-fired power station there, and the coal power station has been decommissioned.
"There are six cooling towers, they are the symbol of Didcot, and three of those towers were brought down in a properly-controlled explosion a year ago and the next three are due to be brought down soon.
"Obviously there are large buildings also to be taken down by professional contractors. I don't know if this is related to that."
He said there would have been a number of people working at the site, adding: "I am very concerned there may have been casualties."
Nicola Blackwood, MP for Oxford West and Abingdon, tweeted: "Thoughts with all affected by incident at Didcot Power Station. Strength and thanks to emergency responders."
Didcot A opened in 1970 as a coal-fired power station and was later converted so it could also generate power from natural gas.
It ceased generation in March 2013 and its cooling towers were blown up in July 2014 after dominating the town's skyline for more than four decades.
According to the RWE npower website the total demolition of the site is expected to be complete by the end of this year.
Today's incident comes 16 months since a major fire struck a cooling tower at Didcot B in October 2014. The blaze affected 50 per cent of the station output - supplying a million homes.
- Daily Mail