ULYANOVSKAYA MINE, Russia (Reuters) - Rescuers said on Tuesday hope was fading of finding anybody alive in a Siberian coal mine where 107 people died in Russia's worst mining disaster in living memory.
Rescue units searching for three people still missing braved smoke, gas pockets and collapsed roofs in the wrecked warren of shafts nearly 300 meters (1,000 feet) underground at the Ulyanovskaya mine.
But Nikolai Kutin, head of the commission investigating the disaster, told Rossiya television the chances of finding any survivors had diminished in the mine, where a gas explosion on Monday morning killed most of the victims outright.
Distraught relatives, many clutching death certificates, wept outside a morgue in the nearby city of Novokuznetsk as they waited their turn to identify the dead.
Guards barred most journalists from getting within sight of the mine complex, which is surrounded by birch forests and soot-blackened snow. Only state-run television was allowed access.
President Vladimir Putin announced a day of mourning on Wednesday for those who died in three Russian disasters which have killed at least 175 people over three days.
Putin began a government meeting in Moscow with a minute's silence for the dead miners -- as well as 62 people killed overnight in a fire at an old people's home near the Black Sea and six who died in a weekend plane crash.
"You have to do your best to investigate the reasons at the highest level ... and to draw corresponding conclusions," Putin told Prime Minister Mikhail Fradkov.
In a separate message of condolence, Putin said the mine accident "echoes in the hearts of Russians with pain".
Officials said failure to follow safety rules was the most likely cause of the disaster. The Prosecutor-General's office said a criminal case had been opened for manslaughter caused by breaching safety rules.
Local rescuers said 107 people were confirmed dead and the fate of three others remained unclear. Ninety-three people were brought safely to the surface.
Emergencies Minister Sergei Shoigu, sent by Putin to oversee the rescue, said the blast was caused by methane or coal dust.
Officials took victims' bodies to the morgue in the city of Novokuznetsk, 60 km (37 miles) north of the mine. Hundreds of relatives huddled outside the morgue.
One man told Reuters his son, Nikolai, had died in the mine where he worked for seven years. He left an infant daughter.
Local authorities declared three days of mourning, cancelling entertainment events and flying flags at half mast.
German Chancellor Angela Merkel, current holder of the EU presidency, expressed dismay in a message of condolence.
Among the dead was a visiting Briton, who was doing a coal reserves audit underground when an explosion wrecked the mine.
Accidents in Russia's often-antiquated mines are frequent but the Ulyanovskaya complex was opened only in 2002.
About 3,500 km (2,175 miles) east of Moscow, the mine is at the heart of Siberia's Kuznetsk basin, known as Kuzbass, which holds some of the biggest coal reserves in the world.
The accident is the worst disaster in a Russian mine since another pit near Novokuznetsk, the Zyryanovskaya mine, blew up in December 1997 killing 67 miners.
Local officials said it was the worst Russian mining accident in living memory.
The Ulyanovskaya mine belongs to Yuzhkuzbassugol, Russia's largest underground coal mining firm, which is 50 percent owned by the country's number two steelmaker Evraz.
Evraz's global depositary receipts, a proxy for shares, fell 2.0 percent on Tuesday to $31.11 in trading in London.