Rescue teams battled smoke and high temperatures on Monday as they pressed on with the task of tracking down 20 missing miners in a Ukrainian coal mine after a methane explosion killed at least 80 others.

Distraught family members demanded information about victims more than 24 hours after the explosion, which -- with the death toll likely to rise -- was almost certain to be Ukraine's deadliest accident since independence from Soviet rule in 1991.

Thirty miners remained in hospital, one in serious condition, Deputy Prime Minister Andriy Klyuyev told reporters.

The toll for now matched that of post-Soviet Ukraine's worst mining accident in March 2000, when an explosion struck a coal mine near the eastern town of Luhansk.

Klyuyev said conditions had improved at the focal point of the accident 1,250 meters below ground at the Zasyadko mine in Donetsk -- the heart of the Donbass coalfield.

There is smoke, but the temperature has fortunately fallen to 51-52 degrees (124-126 Fahrenheit), Klyuyev said. Rescue teams are removing blockages. The mine's work areas are being restored.

Only isolated fires were still burning underground.

The deputy prime minister, who heads a commission of inquiry into the accident, had earlier reported worsening conditions overnight, with a fire raging and temperatures rising sharply.

President Viktor Yushchenko, on a tour of the mine, vowed Ukraine's coal industry would continue to operate and he told workers starting their shifts elsewhere in the large pit that officials would investigate the tragedy to improve safety.

What happened here is an indictment for all levels of authority, for the entire country. It is a humiliation for everyone ... We will draw lessons from it, he told miners clad in overalls, their underground lamps hanging at their sides.

The priority must be to ensure safety in the workplace.

PROBE

He said the Zasyadko mine, one of Ukraine's most efficient and profitable, had made advances to reduce the risk of methane gas. An investigation would show what had gone wrong.

The first funerals of about 20 identified miners were scheduled for Tuesday, declared a country-wide day of mourning.

Trade union officials have since Sunday's explosion said there is little chance of finding survivors.

By mid-morning, more than 100 distraught relatives awaiting news of missing miners pushed their way into the office of the director and interrupted a meeting chaired by Klyuyev.

We demand at least some sort of information! shouted Olga, in her 50s, her face ashen.

We've been waiting for more than 24 hours and all we get are promises. No one is telling us anything.

Officials read out a list of identified victims. Klyuyev told relatives the fire was hampering rescue work and that officials were doing their best to keep relatives informed.

The group left the office within half an hour, with medics attending to several clearly under stress.

Miners at the pit earn wages equal to about $1,000 a month, more than three times national average pay. Many were openly shaken by the accident.

After an accident like this, lots of miners quit and I'm thinking about it too, said one, identifying himself as Nikolai. Why should I do this? I live alone with my daughter. What happens if I end up getting killed?

Other industrial sectors in Ukraine have also been plagued by accidents causing loss of life or damage -- including the derailment of a train carrying phosphorus in July and a gas explosion killing 20 people in an apartment block last month.

Ukraine