Later, a second explosion killed the four rescue workers, said Ilie Paducel, mayor of the town of Petrila where the mine is located.
Hundreds of relatives gathered at the mine after the first explosion, Realitatea TV reported. Romanian President Traian Basescu said he would travel to the site later Saturday.
Mine officials said the explosions were believed to have been caused by an accumulation of methane gas. Officials have banned anyone from going down the mine for the next 48 hours.
Eight injured miners are being treated for burns. Officials said about 100 miners were working at the time of the first explosion The mine in the Jiu Valley employs about 1,500 miners.
