Officials in China’s southwestern megacity of Chongqing were called to a video conference to address mine safety breached following the deaths of 23 workers at the Diaoshuidong coal mine.

Reuters reported that the officials have ordered a crackdown on breaches of mine safety and were told to undertake thorough reforms after the deaths at the Diaoshuidong mine, which was caused by the buildup of deadly levels of carbon monoxide in the shaft.

There have been no reports of arrests, although a full investigation has been launched into the Dec. 4 disaster. One miner was rescued from the mine, where the death toll had originally been believed to be at least 18.

Miners were reportedly dismantling equipment in the mine, which had been closed two months earlier and may have lacked the ventilation systems needed to clear the gas that leaks from the coal seam.

China’s coal mining industry used to be the world’s deadliest, suffering more than 5,000 fatalities a year from explosions, floods and gas leaks. Safety improved dramatically after authorities overhauled the industry starting about 15 years ago, boosting supervision and closing most smaller, more dangerous operations.

The video call meeting was convened at the order of the Cabinet’s occupational safety office, underscoring the central government’s determination to avoid a return to the frequent disasters of the past. Attendees were told mine safety had been deteriorating for several months, citing also a Sept. 27 carbon monoxide poisoning case in Chongqing that killed 16 miners.