Russia's emergency situations minister, Sergei Shoigu, says time is running out to rescue people from beneath the rubble of a collapsed food market in eastern Moscow. At least 56 people died when the entire roof caved in at dawn. But rescue workers say 10 survivors have been spotted amid the debris.

Rescue workers are using pick-axes and sniffer dogs to comb through the steel and concrete wreckage of the roof collapse, as anxious bystanders and relatives look on.

Some survivors are reported to be contacting family members, by mobile phone, to try and pinpoint their position for rescue. Others are said to be making muffled cries for help.

The early morning accident coincided with the beginning of a national holiday honoring Russia's armed forces and could have been far worse, if the market had been open to shoppers.

Moscow Mayor Yuri Luzhkov visited the site to oversee rescue operations, which are taking place amid heavy snow and fog. In remarks broadcast on Russian television, Luzkhov told reporters there is no reason to believe terrorism is responsible for bringing down the 2,000-square-meter roof.

Mayor Luzhkov says investigators are focusing on three possible causes of the collapse: faulty maintenance, a build-up of heavy snow, or errors in the buildings design.

It is the second major collapse of a roof in Moscow in as many years.

In 2004, the roof of the popular Transvaal water park collapsed, killing 28 people. An investigation into that incident is still underway, but is likely to be revived by word that the same architect also built the market affected in this latest collapse.