(IDEX Online) - The Angolan diamond mine blamed for a toxic tailings leak that turned rivers red says the discharge did not contain any hard metals.Catoca accepts that it accidentally released sand and clay into tributaries of the River Congo in July.But it says independent tests it commissioned on water samples have since shown no evidence of toxic hard metals, according to a Reuters news report.Officials in the neighboring Democratic Republic of Congo (DRC) said at the time that 12 people died and 4,400 were taken ill as a result of the pollution.It also said dead fish floated to the surface and two hippopotamuses died. There were reports at the time that the water contained iron and nickel.The Sociedade Mineira de Catoca (Catoca Mining Company), which operates the mine, is jointly owned by Alrosa and Endiama.In a statement cited by Reuters, the miner said: "Samples taken from wide-ranging sources by independent laboratories confirm that at no point have there been any heavy metals present in river water flowing from the tailings basin."Pictures, courtesy Congo Basin Water Resources Research Centre, show red river water and dead fish.