MONTCOAL, West Virginia - Rescue teams were still holding out hope for four workers missing in a coal mine where a massive explosion killed 25, but officials said on Tuesday that the chances were slim that the miners survived.

The suspended rescue mission would resume after bore holes could be drilled to allow for toxic gases to be ventilated from Massey Energy Co.'s sprawling Upper Big Branch mine about 50 km south of Charleston, safety officials said.

"All we have left is hope, and we're going to continue to do what we can," said Kevin Stricklin, a US mine safety official.