The men were killed by Tuesday's explosion more than a kilometer (3,280 feet) below the surface at the Halemba mine in southern Poland. There were no survivors.

"This brings to an end this very sad day," said Zbigniew Madej, spokesman for the state-run Coal Co., at the scene. "Nobody has a sense of relief, but rather a great weight on their heart."

President Lech Kaczynski declared a period of national mourning to last through Saturday, and prosecutors said an investigation was under way.

Six of the bodies were recovered shortly after the explosion and the remaining ones were located after rescue efforts resumed in the night, Madej said.

Jan Gawra, one of 220 miners involved in the rescue attempt, emerged from the mines after digging through the night, his face and clothes black with coal dust.

He said he had worked for 22 years with some of the men whose bodies he helped recover.

"I didn't want to meet with them in this way," said Gawra with a deep breath. "We knew who was down there but we couldn't tell who was who. They were too burned for that."

The search had to be suspended for most of Wednesday when rescue teams encountered high concentrations of gas that they feared could cause a second explosion.

It resumed shortly before midnight, and the teams found the bodies after digging through hundreds of meters of rubble for more than three hours, Madej said.

In addition to bringing down the rubble, the methane gas explosion would have produced temperatures of some 1,000 Celsius (1,800 Fahrenheit), Madej said.

"Rescuers were working in extremely difficult conditions," said Zbigniew Goldstein, a main adviser to a mine rescue center based in nearby Bytom. "We had methane, we had poisonous gases, high temperatures, high humidity, water threats, structural changes after the explosion. Everything that can happen down there."

It may take some time to determine whether the miners were killed in the initial blast, by the cave-ins, or whether they died afterward, rescue officials said.

Hundreds of red and white candles burned outside the entrance to the mine complex through the night, and family members prayed at the nearby shrine of St. Barbara, the patron saint of miners, before the announcement that there had been no survivors.

After the news, a young woman left the canteen where the miners' loved ones gathered during the two-day ordeal, sobbing as two other women supported her on either side.

President Kaczynski, who surveyed the site on Wednesday and met with grieving family members, has pledged a full investigation. The government has also promised financial assistance for the bereaved and a review of safety at all Polish mines.

Michal Szulczynski, a spokesman for regional prosecutors, said his office had opened an investigation and was questioning witnesses, including Coal Co. officials.

The miners, aged between 21 and 59, were attempting to retrieve equipment from a shaft that was closed in March because of dangerously high gas concentrations.

The Coal Co. said equipment worth 70 million zlotys (US million; euro17 million) was left behind, and the team hit by the explosion had been sent in to retrieve it under the supervision of specialists.

Labor unions complain that a lack of investment and massive layoffs in recent years have resulted in falling safety standards at the nation's mines.

The nearly 50-year-old Halemba mine, located in the heart of the Silesia industrial region, is one of the oldest in Poland, and has a record of serious accidents.

It is the worst mining disaster to hit Poland in nearly three decades, and one that hit an economically depressed region that has already witnessed tragedy this year. Just 10 kilometers (6 miles) away, a Polish exhibition hall collapsed during an international trade fair on Jan. 28, killing 65 people and injuring more than 160.