BEIJING, April 17 (Reuters) - A pit explosion in north China has trapped 33 workers underground, Xinhua news agency said on Tuesday, chronicling the latest tragedy to hit the world's deadliest coal mining industry.

"Their condition is unknown ... Rescue work is under way," it said without providing details of Monday's accident in Baofeng county in central Henan province.

A total of 4,746 Chinese coal miners were killed in thousands of gas blasts, floods and other accidents in 2006 as mine owners pushed production beyond safety limits in the face of robust demand and profits. Another 661 were killed in the first three months of this year, down 15.6 percent from a year earlier, but there was a succession of cover-ups of fatal accidents in March, state media said, blaming mine owners and local officials.

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