A major incident has been declared and several casualties feared after reports of a loud blast at Didcot Power Station.
Six ambulances and two air ambulance have been sent to the site in south Oxfordshire, South Central Ambulance Service said.
A spokesman said: “We are describing it as a major incident.” He added that he thought there would be casualties.
Photographs from the scene showed a large chunk of the former coal-fired Didcot A site has collapse. The plant shut in 2013.
Thames Valley Police said it was called to the site at 4pm.
“Officers are at Didcot Power Station at an incident with other emergency services. Further details will be released in due course. #Didcot,” the force tweeted.
The site is home to a combined coal and oil power plant, which has been closed and partly demolished.
No demolition activity had been scheduled for today.
It comes 16 months since a major fire struck a cooling tower at Didcot B in October 2014.