Four people have died at the Ukraine coal mine where 101 people were killed in November in the country's worst mining accident, officials say.
Most of Ukraine's mine disasters are caused by methane gas
Ukraine's Mining Inspectorate said the four men were maintenance workers trying to clear the Zasyadko mine in the eastern Donetsk region.
Thirty-seven miners were helping the maintenance team. One is missing.
Sunday's explosion at the mine followed another on Saturday in which more than 40 people were injured.
Ukraine has had a series of mining accidents since the collapse of the Soviet Union in 1991.
In September 2006 a gas leak at the Zasyadko mine killed 13 miners and injured dozens more.