Investigators are still at the scene, which goes as deep as 1,400m below the North Sea
A man has been killed after a "sudden and powerful release of gas" at one of Europe's deepest mines.
The mine in Boulby, East Cleveland, produces potash, a key ingredient in making fertiliser. It is 1,400m deep and stretches out far under the North Sea.
ICL UK, which operates the mine, said the gas "blow-out" took place in the early hours of Friday morning.
All other workers were safely evacuated from the site and mine inspectors informed of the blast, the company said.
The emergency services and the mine's rescue team are working at the scene.
Cleveland Police said officers were alerted to the incident at around 5.20am.
The force confirmed the fatality and said officers remained at the scene.
"We are working to understand the circumstances surrounding the incident," it said in a statement.
Earlier, Labour MP Tom Blenkinsop, who represents Middlesbrough South and East Cleveland, said: "There has been a serious incident believed to be a gas explosion and we are waiting for further details about what has happened."
He added his "thoughts and prayers" were with the workforce.
In April, seven workers were taken to hospital for checks following an underground fire at the mine.
Last year the firm announced job losses in a "significant restructuring" of its operations, including moving from producing potash to Polysulphate fertiliser.