A gas blast injured nine people Wednesday at a coal mine in the western Slovak town of Novaky, rescuers said.
"Four of them are in critical condition," Alena Krcova, a spokeswoman for the rescue services, told AFP.
No one else was present at the mine when the incident occurred at 4:30 pm (1430 GMT), according to mine spokeswoman Adriana Sivakova.
Two of the injured are Polish while a third is Ukrainian, Prime Minister Eduard Heger told journalists after arriving at the scene.
"There was burning of accumulated methane. Our miners suffered burns," mine general director Stanislav Gursky told AFP.
"We do not know what sparked the flames... We will launch an investigation," the head of the Hornonitrianske Bane Prievidza mining company added.
According to a government resolution adopted in 2019, Slovakia was due to stop coal mining by the end of this year, in line with European climate goals.
