Montcoal, W.Va. - Grieving relatives began burying victims of the Upper Big Branch coal mine disaster Friday as rescue crews ventured back into the blast-damaged shaft for another agonizingly slow, dangerous and probably hopeless search for survivors.

It was their fourth attempt to find the four miners missing since Monday's explosion killed 25 others in the nation's worst underground disaster since at least 1984. During the previous rescue attempts, searchers were forced to withdraw by dangerous gases and the risk of fire or explosion.

"We are praying for a miracle," President Barack Obama said in Washington.

Rescuers acknowledged that was what it would take for the miners to have made it to a refuge chamber stocked with food, water and enough oxygen for several days.

On Friday morning, rescuers made their way about 1,000 feet underground and five miles into the mine to examine one of the chambers, but no one was inside and smoke forced them to turn back before they could check a second one that would represent the last hope the four were alive.

"We're confident that if they got in there, and they were alive, that we would be able to still rescue them," said Kevin Stricklin of the federal Mine Health and Safety Administration.

The area was flushed with nitrogen and crews headed back inside in the afternoon for what was likely to be a three- or four-hour trip to the chamber, an expandable box activated by opening a door and pulling a lever.

Officials had hoped to lower a camera into the mine to see if the chamber had been used, but the hole was drilled slightly off target, and Stricklin said they would not have been able to see anything.

More than 300 people packed the Mullens Pentecostal Holiness Church for the funeral of Benny Willingham, a 61-year-old miner who was five weeks from retiring when he died.

He was saved 19 years ago this week, said Rev. Gary Pollard, pastor of the Mullens Family Worship Center, where Willingham was a deacon. The two had weekly 45-minute talks - about God, about Christian living, about their families and friends - every Sunday morning for the past five years.

Pollard said the last time he saw Willingham, the miner's words were almost prophetic: "If I die tomorrow, I've lived a good life."

"He wasn't the biggest man in town. He didn't have the stature of some of you sitting here," said Pollard, whose own church across town was too small for the crowd. "But if you could see the size of this man's heart, you'd see a giant."

Willingham was dressed in a red shirt in the open coffin, jet-black hair and mustache neatly combed, family snapshots tucked in the satin around his head and shoulders. The image of a pick, shovel and miner's helmet was embroidered in the fabric along with his name, and a flag draped the lower half of his coffin in a nod to his service during the Vietnam era in the Air Force.

Three Air Force veterans, friends of his for more than 40 years, traveled with their wives from Ohio, California and North Carolina to say goodbye.

"That's astonishing," said the Rev. Lewis Arnold, pastor of the host church, "but that is Benny Willingham."

Officials suspect the blast was caused by a buildup of methane gas.