Hopes were fading Monday for the remaining seven Chinese miners still missing after a deadly gas leak over the weekend that left 30 dead.
The State Administration of Work Safety announced on its website that as of 6 a.m. local time (5 p.m. ET on Sunday), rescuers had found another four bodies, raising the death toll to 30.
The accident occurred early Saturday in a pit owned by Pingyu Coal & Electric Co. Ltd in Yuzhou city in central Henan province. Officials said 239 people escaped.
The remaining seven are unlikely to be alive, local media said.
"Based on experience, the remaining miners could be buried in coal dust, so the chances of survival are slim," said Du Bo, deputy chief of the rescue operation headquarters, according to the Xinhua news agency.
Police tightened security around the mine, with dozens of officers blocking entry points and forcing reporters to leave the area. Grieving family members and friends, who had crowded around the mine entrance a day earlier asking for information were nowhere to be seen.
China's mines are the deadliest in the world, with more than 2,600 people killed in coal mine accidents in 2009 alone. The country's lax safety rules and enormous demand for coal to power its economy have contributed to high casualties.
An initial investigation found that 6 million cubic feet of gas rushed out, the official Xinhua News Agency reported earlier. The gas leak generated enough force to throw 2,500 tons of coal dust into the mine pit, it said.
The gas wasn't specified, but methane is a common cause of mine blasts. In this incident, there was no explosion but mine safety officials said they were afraid the missing men may have suffocated and been buried by coal dust.
"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," said Liu Wenbin, a deputy chief engineer of the company that owns the mine, Xinhua reported. He was in the pit at the time of the blast.
Another gas leak in 2008 at the same mine killed 23 people.
The Saturday accident occurred after Chile's dramatic rescue last week of 33 miners trapped for more than two months underground. Chinese media had very detailed coverage on the Chilean rescue, but information has been very limited on the Chinese mining accident.
Mining deaths have decreased in recent years as China closed many illegal mines or absorbed them into state-owned companies, although deaths jumped in the first half of this year.