Rescuers said Monday with the discovery of more than 20 bodies Monday, the death toll of Sunday's gas explosion at the Chenjiashan Coal Mine in northwest China's Shaanxi Province rose to about 50. The definite number is not available.

Forty-three injured miners, who suffered from serious burns, carbon monoxide poisoning or scratch injury, have been sent to local hospital, of which 15 seriously injured were moved to a better-equipped hospital in Tongchuan, where the mine is located.

Most of the injured are out of danger, except that a severely-injured is still in a critical condition, said Song Zhigang, deputy director of the Tongchuan Mining Administration.

There were 293 miners working underground when the gas explosion happened at coal pits some 8,000 meters away from the coalmine entrance and 127 others were rescued. The escaped miners were mainly worked near the entrance.

Most of the trapped workers are local residents and the rest are from the neighboring Henan Province, Song said.

Even though the main ventilation system has been repaired on Monday morning, those at No. 415 and No. 416 working areas, where the explosion occurred, however, were still not workable, making the places unsafe for rescue staff.

To make the situation worse, rescuers who came back from the tunnels said they saw light blue smoke underground. Experts said the coal bed could be on fire.

"This greatly hobbles the rescue work, but 12 rescue teams with96 members each are working around the clock to rescue the trapped workers," Song said.

Families of the trapped miners were gathering in great anxiety around the mouth of the mine or the hospitals, waiting for news about their husbands, fathers, sons or brothers, even though the temperature dropped below zero.

"My youngest child Pang Yuming entered the tunnel on Saturday night and he is still trapped inside," said 66-year-old Nie Ruan'ewith a blank look.

"As a tunneling worker, he must stay in the working area near to the explosion site. I really don't know if he can get out of the tunnel alive," said the mother.

An investigation team sent by the State Council, China's cabinet, has arrived at the mine on Sunday night and visited the injured miners on Sunday.

You Quan, deputy secretary-general of the State Council, said local officials should try every possible means to search for the missing, take care of the injured and handle well the aftermath.

"It is also necessary to set up a sound information releasing system, letting the public know about rescue work in time," said You, who is also head of the investigation team.

The Chenjiashan Coalmine is a state-owned venture under the jurisdiction of the Tongchuan Mining Administration. It has more than 3,400 employees and produces 2.3 million tons of coal a year.

The coal mine is a high-gas-density colliery and a gas explosionkilled 38 in this mine in April 2001.

To improve its anti-disaster capability, the coalmine introduced an underground fire monitoring system in last November,but just a week before this explosion happened, a fire broke out in the mine on Nov. 23.

The Shaanxi provincial government issued an urgent notice on Monday, requiring the province's all mines with high gas density to halt operation for safety examination.

This is the second fatal colliery gas explosion causing heavy death toll in a state-owned coal mine over the past 40 days. Previously, a gas explosion happened at the Daping Coalmine in central China's Henan Province on Oct. 20, killing 148 and injuring 32.