An explosion in a northern Chinese coal mine (search) caused a massive cave-in that killed 16 miners and trapped another 11 miners below ground, officials and the government's Xinhua News Agency reported Thursday.

The blast ripped through the Xiangyuangou No. 2 mine in Shanxi province's (search) Jiaocheng county on Wednesday afternoon as 83 miners were at work in the shaft, Xinhua said.

Fifty-six miners escaped or were rescued but 11 remained unaccounted for, Xinhua said. Six rescued miners were injured, it said.

An official with the Shanxi provincial production safety bureau said the blast badly damaged the ceiling of the shaft, trapping the miners behind tons of rubble.

"Rescuers are working as hard as they can to dig-out the tunnel, but progress has been slow," said the official, who refused to give his name or title.

"We still think we have a pretty good chance of rescuing them alive, as long as they weren't badly hurt by falling rocks or burnt severely in the gas explosion," he said.

Mine explosions are a regular occurrence in Shanxi, one of China's key coal producing regions. Provincial officials earlier this month announced plans to limit numbers of miners working underground at any one time and restrict the total number of mines in operation.

No timetable was given for enforcement of the new plans and similar announcements in the past have done little to improve mine safety.

China's mines are the world's deadliest with fatalities reported almost daily from explosions, floods, cave-ins and other mishaps.

A man who answered the phone at the Xiangyuangou mine's administrative office wouldn't give further details about the accident or rescue effort.

However, he said the mine belonged to the local government and produced about 600,000 tons of coal each year.

"It's not a small mine," said the man, who wouldn't give his name.