The death toll from an explosion at a Czech coal mine has risen to 13, among them 11 Poles and two Czechs, the OKD mining company said on Friday. The state-run firm had said earlier that a methane blast more than 800 meters underground devastated areas of the CSM coal mine near the town of Karvina on Thursday, Reuters reports. OKD Managing Director Boleslav Kowalczyk said the search of the scene had had to be abandoned due to conditions in the shaft. The incident is the worst mining accident in the Czech Republic since 1990, when 30 miners died in a fire at a mine near Karvina. OKD said most of the victims and injured were Polish miners provided by the ALPEX company.