A Russian-owned mining company, Severstal Liberia Iron Ore, has more than doubled its estimate of iron ore at its Putu mine in the south-east of Liberia following an independent audit. The reserves estimate has been raised from 1.08bn tonnes with an Fe content of 37.6% to 2.37bn tonnes with an Fe content of 34%. This estimate could increase further, as exploration of the deposit has continued and a pre-feasibility study is expected by September 2012, when the capacity of the operation will be known more precisely. Severstal has invested US$30m in the pre-feasibility study following the signing of a 25-year mineral development agreement with the government in September 2010 (December 2010, The domestic economy). It holds a 61.5% interest in the project, with the remaining 38.5% held by a company listed on London's Alternative Investment Market (AIM), African Aura. It is likely to cost up to US$2.5bn to put the project into production, which could begin in 2017. The government is expecting royalties of US$1.6bn in the first 20 years of operation at the mine, which should produce at least 20m tonnes of magnetite concentrate annually.