By Fuat Kabakci

BEIJING

Seven workers remain trapped in a coal mine in central China's Henan province after a roof caved in overnight killing five people.

State news agency Xinhua reported a local safety watchdog as saying Thursday that the collapse occurred at 9 p.m. Wednesday (1300GMT) when Xingyu Coal Mining Co. Ltd. workers were expanding a pipe way in a Dengfeng city colliery, causing a gas outburst.

Three of those who died were rescuers.

Work is continuing to free those trapped inside

Chinese mines are among some of the most dangerous in the world due to lax regulations and poor operating procedures.

In recent years, the country has produced more than one-third of the world's annual coal output, but accounted for more than two-thirds of global mining deaths annually, according to the Mining Technology journal.