A court in southeastern China's Fujian province has ordered the country's biggest gold miner, Zijin Mining Group, to pay a criminal fine of $4.6 million for toxic mine spills that highlight the challenges of policing heavy polluters with close ties to local authorities.

A company vice-president and the manager, deputy manager and environmental protection officer of the mine were detained in connection with the spills at the Zijinshan Gold and Copper Mine nearly a year ago, which poisoned a river, killing off fish and devastating the area.

Longyan City Intermediate People's Court rejected the company's appeal against an earlier ruling fining it 30 million yuan ($4.6 million) for a "serious offence related to environmental pollution," Zijin Mining said Wednesday in a notice to the Hong Kong Stock Exchange.

The court ordered the company to pay the balance remaining after taking into account administrative fees already paid, and five defendants were given prison terms of between 3 years to 4 1/2 years in the case, it said without specifying details.

As public awareness grows of the pervasive damage done to the environment over more than three decades of rapid industrialization, authorities have been tightening controls and shutting down some of the heaviest polluters.

But fines imposed are often just a pittance for big, government-backed companies. Zijin Mining reported 27.8 billion yuan ($4.3 billion) in revenues in 2010, and 4.8 billion yuan ($738.5 million) in profit.

The ore processing facility at the Zijinshan open-pit mine was using a leeching process that employs highly toxic cyanide, according to reports in the Chinese media and information on the company's website.

Zijin publicly apologized and acknowledged a waste pond at the mine was improperly built and operated, causing accidents on July 3 and July 16.

Weeks later, on Sept. 21, a tailing dam at another Zijin facility, the Yinyan Tin Mine in southern China's Guangdong province, collapsed in torrential rainfall brought on by a typhoon.

A local Environmental Protection bureau notice put the direct economic toll from the Zijinshan accidents at almost 32 million yuan ($4.9 million). That notice, issued late last year, also ordered Zijin Mining's chairman, Chen Jinghe, to pay a fine equal to half of his annual income from the company, or 705,997 yuan (about $108,600).

In its recently issued 2010 annual report, the company said it had "seriously learnt the lessons" from the disasters and would make safety and environmental protection priorities.

But Chinese media have questioned Zijin's links with local officials, many of whom own stock in the company.