(CNN) -- Rescue officials say five more bodies have been found after a coal mine gas leak in central China's Henan province, bringing the death toll to 26 as of Sunday morning, China's state-run Xinhua news agency reported.

Rescuers were battling to reach the 11 miners still trapped underground, but chances for them to survive were very slim, said Du Bo, deputy chief of the rescue headquarters, the news agency said.

"Based upon past experience, the remaining 11 miners could be buried in coal dust, so the survival chances are frail," Du was quoted as saying.

More than 2,500 metric tons of coal dust smothered the pit after the gas leak, which hampered the rescue, Du said, according to Xinhua.

The gas outburst happened Saturday morning when 276 miners were working underground in Yuzhou City. A total of 239 workers escaped, Xinhua said.

An initial investigation showed that 173,500 cubic meters of gas leaked out in the accident.

Liu Wenbin, a deputy chief engineer of the company that owns the mine, was in the pit when the accident happened and organized the escape, Xinhua reported.

"At around 6 a.m., I felt there was something wrong with the airflow in the shaft, and one of the team captains told me he also felt it and had already reported the problem," Liu said.

The mine is owned by Pingyu Coal & Electric Co. Ltd., a company jointly established by four investors, including Zhong Ping Energy Chemical Group and China Power Investment Corp., according to Xinhua.

The same mine reported another explosion in August 2008, that killed 23 miners.

China has one of the world's deadliest records for miners, with poor safety standards accounting for thousands of deaths each year.

Earlier this week, China announced it had closed 1,355 small coal mines this year, Xinhua said. The effort was part of a larger plan by the National Energy Administration to restructure the mining industry to prevent deadly accidents and reduce greenhouse gas emissions, the news agency said.

CNN's Eve Bower contributed to this report.