On Tuesday, rescuers will resume a search for four missing workers after a mine blast in West Virginia killed 25 people on Monday—the worst U.S. mining disaster in more than 20 years. The rescuers will drill holes into the mine shaft, in order to allow toxic gases to be ventilated. The mine operator, Massey, has a history of not properly ventilating combustible methane gases. “All we have left is hope, and we're going to continue to do what we can," said Kevin Stricklin, an administrator for the federal Mine Safety and Health Administration. "But I'm just trying to be honest with everybody and say that the situation does look dire." At the White House Tuesday morning, President Obama gave his "deepest condolences" to the victims and their families, who he hopes can "find comfort in the hard days ahead." He said that "the federal government stands ready to offer whatever assistance is requested."