An early morning explosion Monday in an apartment building in Russia has left at least two dead and dozens missing after the building partially collapsed, the New York Times reports. Officials suspect a gas leak as the cause of the 6am blast, which damaged nearly 50 of the 110 units while most of the occupants were still asleep. The explosion in Magnitogorsk, located more than 1,000 miles east of Moscow in the Ural Mountains region, is believed to have taken place on the first floor, which then caused the seven floors above it to collapse, per the BBC. The search for survivors has taken on special urgency due to the freezing temperatures, hovering near zero. (More Russia stories.)