Shares in Manchester United rose 1% on Thursday in the first trade since the club revealed that one of its biggest investors had increased his stake to almost 6%.
Malcolm Glazer, owner of American football team the Tampa Bay Buccaneers, now owns 5.92% of the club, making him Manchester United's fifth biggest investor.
The club - one of the best known global sporting brands - is thought to be in the sights of a number of potential buyers.
There were rumours earlier this year that Mr Glazer was weighing up a bid for the club, possibly in conjuction with three other shareholders - Irish horseracing tycoons John Magnier and JP McManus, and Dutch television entrepreneur John de Mol.
More recent takeover speculation has centred on an unidentified Russian billionaire and a Middle Eastern businessman, also unnamed.
Rumours of a foreign buyout have gathered pace following the surprise takeover of Manchester United's premiership rivals Chelsea by Russian oil billionaire Roman Abramovich.
However, Manchester United would not come cheap, with an estimated price tag of about £600m ($960m).