An illegal mining practice was the cause of a southwest China colliery accident Saturday which left 30 people dead, a senior official in charge of the country's work safety organization said.

"The May 30 accident is a major safety accident caused by an illegal practice which violated the mining rules," said Luo Lin, chief of the State Administration of Work Safety (SAWS) on Sunday.

Luo disclosed that the State Council will set up a special investigation team to look into the explosion.

Zhao Tiechui, head of the State Administration of Coal Mine Safety (SACMS), pointed out that an excessive amount of explosives directly triggered the accident.

"Coal mine owners put the emphasis on accelerating construction instead of work safety," said Zhao, adding that workers should have been evacuated before detonation.

"The mine's managers didn't evacuate workers in time," said Zhao.

The police detained three people including the coal mine's owner, chief engineer and project manager. Their names have not yet been released.

The explosion occurred around 11 a.m. at Tonghua Coal Mine in Anwen Town of Qijiang County, when 131 miners were working about 1,000 meters underground. One hundred and one miners were rescued, although 59 were injured, including four in serious condition.

Another 30 miners were killed.

The Tonghua Coal Mine, with a history of more than 50 years, is affiliated with the state-owned Songzao Mining Bureau of Chongqing. The colliery's designed production capacity is 300,000 tonnes per year, which now has been expanded to 600,000 tonnes.

(Xinhua News Agency May 31, 2009)