Published: Apr 09, 2010 10:43 AM EDT

MONTCOAL, W.Va. (AP) - Signs of fire forced rescue crews to retreat again early Friday before reaching an underground refuge chamber where they hoped to find four coal miners missing since an explosion that killed at least 25 others.

Federal mine safety official Kevin Stricklin told a news briefing that rescue teams working their way through the wrecked mine encountered smoke and were ordered out. It was the third time since the Monday blast that rescuers have had to pull out because of dangerous conditions. "It's very emotional for all the rescuers," Stricklin said.

Families were also on edge, said Gov. Joe Manchin, who briefed the relatives before the news conference. "We had to walk in and explain to them that we had a situation that no one wanted, but a situation that had to be dealt with," Manchin said.

Stricklin said it does not look like rescuers will physically be able to get to the refuge chamber because of the smoke. They may have to depend on cameras to check it out. "The thing that is unknown is exactly where this fire is at," Stricklin said.

Stricklin said rescuers reached a first refuge chamber, stocked with air, food and water, and found it unused. They were on their way to a second chamber when they had to withdraw.