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.