In the March 2020 incident water containing molybdenum ore flowed out of a tailings pond belonging to Yichun Luming Mining Co and into a local river system before eventually spreading hundreds of kilometres downstream.
Tailings ponds or dams are commonly used by mining firms to store waste remnants of ore. They have been under close scrutiny globally since the 2019 collapse of one in Brazil killed around 270 people.
The ecology and environment department in the city of Yichun, in Heilongjiang province, imposed the penalty on Yichun Luming after investigators found it had carried out substandard engineering, made inadequate preparations for emergencies and violated water pollution control laws, The Paper said.
Yichun Luming, a subsidiary of state-run China Railway Resources Group, did not immediately respond to a request for comment.
Up to 117.5 tonnes of molybdenum leaked out in the incident and around 68,000 residents saw disruption to their drinking water supply, said The Paper, which is backed by the Shanghai city government.
The spill was the biggest tailings leak China had witnessed in almost 20 years and needed a tough emergency response, the country's environment ministry said at the time https://www.reuters.com/article/uk-china-tailings-molybdenum-idUKKBN2220O6.
($1 = 6.4790 Chinese yuan renminbi)
(Reporting by Tom Daly; editing by David Evans)