The death toll from a coal mine blast in a separatist eastern region of Ukraine rose to 17 on Saturday, rebel authorities said.

The gas blast on Thursday ripped through the mine in Yurievka village in the self-proclaimed republic of Luhansk, which broke away from Kyiv in 2014 and is run by Moscow-backed rebels.

“The tragedy took the life of 17 miners,” Leonid Pasechnik, the head of the unrecognized Luhansk republic, said on Twitter.

He added that the bodies of all the miners that died have been recovered.

Earlier the death toll accounted to 13, with another four people missing.

Pasechnik called the explosion at the Skhidkarbon mine a “terrible tragedy” and declared April 29 a day of mourning.

Russia’s emergency situations ministry sent mine rescuers to the separatist territory after it requested help, it said in a statement.

The Luhansk news agency said the mine was closed in 2014 due to the conflict between Kyiv’s forces and the Russia-backed separatists, but was reopened in 2018.  

Most of Ukraine’s coal is produced in its eastern region, where the ongoing fighting has cost some 13,000 lives.

Kyiv has tried to boost the operations of other pits under its control in the west of the country.