Chinese officials say an explosion in a coal mine Saturday has killed 21 workers and trapped 16 underground.

The state work safety agency said the mine in the central province of Henan was hit by an explosion Saturday. The mine is owned by the Pingyu Coal & Electric Company based in Yuzhou City.

Authorities said rescue workers were trying to reach the trapped miners, but it was not known whether they are alive. State-run television reported the rescue workers were hampered by excessive gas levels in the mine and chunks of coal that had fallen into the mine shaft because of the blast.

More than 2,600 people died in mining accidents in China last year.  That was down from previous years, but officials say there were more deaths in mine accidents in the first six months of 2010 than in the same period last year.

On Thursday, a new regulation came into effect requiring mine supervisors to go underground with workers or to pay large fines.  Companies could be fined up to $750,000 for not complying with the new rule.

Premier Wen Jiabao ordered mine managers in July to begin spending time in the shafts with workers in an effort to make the bosses more aware of safety issues.  However, Chinese state media have reported cases of managers appointing substitutes in order to avoid Mr. Wen's order.

State media reported Thursday that China has shut down more than 1,500 small, illegal coal mines this year as part of an effort to improve safety standards.

Some information for this report was provided by AP, AFP and Reuters.