The country's top environment and emergency management apparatuses, together with Heilongjiang provincial government, on Monday set up a joint team to investigate over the largest leakage of mine tailings in the country in the past two decades.

The joint team will look into the causes of the incident, which occurred on March 28 at the tailings pond of a molybdenum mine of Yichun Luming Mining Co in Yichun, Heilongjiang province, in a thorough manner.

Aside from identifying the causes, it will come up with suggestions for rectification and future precautionary measures in its efforts to "effectively ramp up prevention and control of environmental risk", according to a media release from the Ministry of Ecology and Environment.

Part of the tailings entered a nearby watercourse that finally empties into Heilongjiang River, or the Amur River as it is called in Russia, via Songhua River.

The incident resulted in "the largest leakage of mine tailings, the emergency handling of which is the most challenging, in the past 20 years". The task to remediate its environmental damages is confronted with considerably arduous difficulties, the Monday release said.

It said, thanks to efforts of local authorities and a work group dispatched by the ministry, polluted water had been prevented from entering Songhua River after emergency handling that lasted for a fortnight.

At 3 am on April 11, the polluted water was found have reached national environmental standard when they were 70 kilometers from Songhua, it said.