More than $25 million in Fairfax shares have been bought in one transaction, fuelling speculation mining magnate Gina Rinehart is increasing her stake in the media company.

At 1228 AEST on Thursday, 42 million Fairfax shares were bought in one transaction, at a price of 60 cents per share.

The trade was worth $25.2 million, and represents 1.8 per cent of Fairfax’s total issued shares.

Fairfax shares were trading at 60.75 cents at 1422 AEST.

Comment is being sought from brokers, but there have been reports the shares were bought on behalf of Mrs Rinehart, Fairfax’s largest shareholder.

If Mrs Rinehart was behind the buy, her stake in the company would rise to almost 15 per cent.