Four miners have been confirmed dead, after a coal mine tunnel collapsed Tuesday afternoon in northeast China's Liaoning Province, the local authorities said Wednesday. The provincial coal mine safety department said the accident happened at 4 p.m. Tuesday in Caitun Coal Mine in Benxi City, when seven workers were working under the tunnel. Three of them managed to escape, Xinhua reported. The state-controlled coal mine, which turned out 600,000 tonnes last year, was under renovation when the accident happened. The provincial coal mine safety department has set up a working group to investigate into the accident.