MEZHDURECHENSK, Russia — Rescue operations to find 24 workers missing in a Siberian coal mine explosion were suspended Thursday because of fears of a new blast.Nonessential workers and miners' relatives were taken away from aboveground areas around the Raspadskaya mine because of safety concerns. One of the blasts at the mine on Sunday seriously damaged buildings on the surface.The Russian Emergencies Ministry said Thursday that the death toll from the explosions now stands at 66.A ministry official, Pavel Plat, told reporters at the mine that the concentration of volatile methane gas in the mine is rising and that several sizable fires are burning some 460 meters (1,500 feet) underground.Plat said methane concentration at some points in the mine was 7 percent. A concentration of 1 percent is generally considered to be the limit of safe conditions."Our task now is to put out the fires and reduce the gas concentration, and only after this is done will we send people" to the area where the missing miners are believed to be, Plat said.There have been no reports of contact with any of the missing, and prospects for any survivors appear to have all but vanished.Many of the dead were rescue workers who went into the shafts after the first blast late Saturday and were caught in the second explosion Sunday — which was so powerful that it shattered the main shaft and a five-story building at the mine head. The mine is in the Kemerovo region, about 3,000 kilometers (1,900 miles) east of MoscowThere was no information on what set off the blast. Mine explosions and other industrial accidents are common in Russia and other former Soviet republics, and are often blamed on inadequate implementation of safety precautions by companies or by workers themselves.The deadliest explosion in Russia's coal mines in decades occurred in March 2007, when 110 miners were killed.The Raspadskaya mine produces about 10 percent of Russia's coking coal, Vedomosti said, and a long interruption of production could affect Russia's steel industry.