Two long-term supporters of Fortescue Metals Group Ltd (ASX:FMG) have reportedly sold large chunks of their shareholdings in the iron ore miner.

The company says it has received no explanation from its two biggest US shareholders, New York hedge funds Harbinger Capital and Leucadia Capital, about why they have each sold about 30 million shares.

Leucadia told the ASX this week that it sold 30 million shares on February 20 for $US121.5 million, cutting its stake in the company from 9% to 8%.

Having bought the shares at $1.50 each in 2006, Leucadia earned about $90 million from the sale.

Fortescue says that neither Leucadia nor Harbinger have notified the company of their actions.

The Australian newspaper reports that the share sales appear to break a February 2009 pledge that Harbinger boss Philip Falcone is believed to have given Fortescue CEO Andrew Forrest that he would not sell down his stake.

Fortescue Metals Group booked a profit of $626.13 million for the 2009 financial year.