A methane leak in a Polish coal mine set off an explosion that killed 12 miners on Friday, officials said.
Edyta Tomaszewska, a spokeswoman for the state body that oversees Polish coal mining, said the explosion occurred 3,450 feet (1,050 meters) underground at the mine in the southwestern city of Ruda Slaska.
Some of the miners were killed immediately and others died later of burns, Tomaszewska said.
Poland's TVN24 television reported that 38 miners were near the site of the explosion and that 15 were seriously injured.
Interior Minister Grzegorz Schetyna was on his way to the site of the accident and Tomaszewska said mining authorities had opened an investigation into what caused it.
Friday's blast was Poland's most serious mining accident since a methane gas explosion killed 23 miners at the Halemba mine in November 2006.
In June 2008, five miners were killed in a methane gas explosion in a shaft nearly 3,000 feet underground near the town of Jastrzebie Zdroj.
More on: Poland