Pictures circulating on social media show part of a building has collapsed following a loud blast.
One person has died, according to the Oxford Mail.
Rodney Rose, deputy leader of Oxfordshire County Council, told the paper: “I have been told there has been one fatality, but the rest is currently unknown.”
He added the incident has being treated as a “collapsed building, not an explosion” but said there was a bang.
Thames Valley Police and a hazardous response team are at the scene.
South Central Ambulance Service described it as a “major incident” and were callled to the power station at 4pm.
Six ambulances and two air ambulances qwere sent to the scene.
A tweet sent out by Thames Valley Police said: “Officers are at Didcot Power Station at an incident with other emergency services.
“Further details will be released in due course.”
A huge fire at Didcot power station destroyed four cooling towers in 2014.
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