(IDEX Online) - Alrosa is to help revive the only commercial diamond mine in the Democratic Republic of Congo (DRC). The move follows the death of 12 people in DRC from a toxic leak at a diamond mine in which Alrosa holds a 41 per cent stake.DRC has said it will seek compensation in line with the "polluter pays" principle after tailings from the Catoca mine, in neighboring Angola, poisoned tributaries to the River Congo. The water started turning red at the end of July, thousands of dead fish floated to the surface and 12 villagers living near the river died.Alrosa has since signed a memorandum (MOU) of understanding with Bakwanga, known as MIBA, to explore, mine and process diamonds together, according to a Reuters news report. The MOU is understood to make no mention of the toxic leak. At its peak in 1961 MIBA, the Bakwanga Mining Company, produced 16m carats, but it has been badly hit by two wars, widespread corruption, embezzlement, poor management and infrastructure, crippling debt, unpaid workers' wages and a three-year closure following the 2008 financial crash. Current output is estimated at just 500,000 carats a year.DRC was the world's fourth-largest diamond producer by volume in 2019 (14.2m carats) but the vast majority of diamonds are produced by artisanal miners using primitive tools in dangerous and unregulated conditions.Pictures, courtesy Congo Basin Water Resources Research Centre, show red river water and dead fish.