Experts in southwest China's Sichuan Province are investigating the appearance of 26 huge pits in a village within seven days.

The first sinkhole was discovered at midnight of April 27, when a sudden shake and deafening crash awoke the villagers in Yibin City, Chengdu Economic Daily reported yesterday.

The largest pit was 40 meters in diameter when it was discovered and grew to 60 meters across by the next day.

The sinkholes kept expanding in size last week, affecting an area of 0.6 square kilometers. About 290 people living in the affected area have been forced to leave their homes and move into temporary camps.

Some believe the sinkholes could be associated with the karst geography of limestone regions, which can be caused by repeated land subsidence, often as a result of drought or extensive drainage.

In karst regions in China it's known as "Tiankeng," or heavenly pit.

But some villagers blamed the collapse on round-the-clock underground work at a coal mine 15 minutes' drive from the village.

The state-owned coal mine was flooded on April 25. No one was harmed in the accident.

"We will take the responsibility if the pits are caused by our work," said Bian Yajun, an official at the coal mine.