Brazil's largest diversified steelmaker Cia Siderurgica Nacional SA (CSN) said Tuesday that it has raised its stake in north-west Mozambique-focused coking coal miner Riversdale Mining Ltd.
CSN raised its stake from 16.29 percent on November 24 to 17.58 percent February 8, which potentially complicates the US$3.9 billion offer made by Rio Tinto.
Riversdale's current biggest shareholder is Tata Steel, which owns 24.2 percent of Riversdale.