The incident occurred at the RWE npower Didcot A power plant, around 70 miles (113 km) west of London.

The plant closed in 2013 and was in the process of being demolished.

"I can confirm search operations are in progress and that there has been one fatality, five persons have been taken to hospital and three persons are currently missing," Oxfordshire Fire Service Area Manager Mat Carlile said in a statement.

Residents told local media there had been a large rumble, prompting reports there had been an explosion.

Television pictures showed half a large building at the site appeared to have collapsed.

However, emergency services said they were treating the incident as a building collapse and although dust had spread over a considerable area, there had been no hazardous materials inside.

"There has been an incident at our former Didcot A Power Station site," RWE npower said in a statement. "The site is currently being demolished. We are working with our contractors Coleman and Company to establish the facts."

Didcot A, a dual-fired power station which could produce enough power for 2 million households, closed down in 2013 after 43 years of operation.

In 2014, a fire broke out at Didcot B, an operational gas-fired power plant on the same site. No one was hurt but one of two power generation units had to be taken offline.