American sports entrepreneur Malcolm Glazer has increased his shareholding in Manchester United to nearly 10%, the UK Premier League club said.
Man Utd made full year profits of £39m
Mr Glazer owns the Tampa Bay Buccaneers, the Florida-based winners of the Super Bowl American football championship.
Man Utd said Mr Glazer has raised his shareholding to 9.66%.
It is the second time in a fortnight Mr Glazer has bought more Man Utd shares - earlier this month he raised his stake from 5.9% to 8.94%.
Rumours of a takeover have swirled round Man Utd in recent weeks, as several sporting entrepreneurs have increased their shareholdings.
Takeover speculation was sparked by satellite broadcaster BSkyB's decision to offload its 10% stake in the football club.
Irish horse racing tycoons J.P. McManus and John Magnier snapped up BSkyB's stake in early October, taking their joint holding to 23.15%.
That triggered a flurry of speculation that the Irish duo might be preparing a full-blown takeover attempt
Mr Glazer has been named as a possible bidder for Man Utd, as has Dutch TV entrepreneur John de Mol, who took his stake from 3.5% to 4.1% in early October.
Scottish mining entrepreneur Harry Dobson, and Dermot Desmond, the Irish millionaire who owns 21% of Celtic football club, have also been named as possible bidders.
Institutional investors tend to steer clear of football clubs because their financial performance is unpredictable, and most do not make enough money.
But analysts say Man Utd would make an attractive takeover target because, unlike many of its Premiership rivals, the club is free of debt and makes healthy annual profits.
Man Utd's has turned its success on the pitch into a worldwide merchandising operation which generates hefty earnings.