Around 300 fans were involved in a noisy demonstration near the club's superstore before the Premier League match against Stoke City, chanting anti-Glazer songs and brandishing placards.
The Glazers took control of United, England's biggest club, five years ago, but anger has mounted about the size of the debt, estimated at around 700 million pounds.
Many supporters have worn all season the green and gold colours worn by Newton Heath, the amateur club founded in 1878 which became Manchester United.
Hundreds of fans also surged towards the diretors entrance at Old Trafford, although the Glazers did not attend the 4-0 win over Stoke City which proved in vain as United ended the season behind Chelsea.
Greater Manchester Police confirmed that a smoke bomb had been set off but said there were no injuries or arrests.
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