Ineos boss Sir Jim Ratcliffe and Qatari banker Sheikh Jassim will submit new takeover bids after an extended deadline at their request amid chaos on Wednesday night.
Bidders were told they had until 21:00 GMT to submit a second revised bid.
BBC Sport understands that several other proposed investors also made submissions at the time.
It was not immediately clear when the new deadline would be.
Ratcliffe and Sheikh Jassim are the only publicly announced bidders.
Initially on Wednesday night, sources close to the pair strongly stated that they had submitted new bids.
But in the past 48 hours, first the Qatari team and then Ineos submitted a request to investment bank Raine, which conducted the sale, for more time to make a second offer, which was approved.
People close to the talks described the situation as “real-time and fast-moving”, but sources insisted that both Sheikh Jassim and Ineos were committed to a second bid.
However, the twists and turns in the sale process have only heightened concerns among some fans that the American owners, the Glazer family, may decide not to sell the club.
Ineos wants to acquire a combined roughly 69 percent stake in the Glazers, but the Qataris are aiming for 100 percent of the club.
The two sides met with joint officials in early March.
BBC Sport understands United officials recently met eight different potential investors during a 10-day high-level meeting, including representatives of Ratcliffe and Sheikh Jassim.
The size of their initial bids has not been disclosed – both are reported to be around £4.5bn – but they are clearly well below the £500-6bn valuation set by the Glazers, which would break the record £3.71 bn paid for a sports team.
Whether they — or any other potential bidders — can submit an offer that convinces Glazer to sell is the next key question.
If not, with United’s fortunes improving significantly under manager Eric ten Haag in recent months, the Americans may well decide to keep the club and may instead consider a minority sale to the United States. Hedge fund Elliott Investment Management and others.
The Glazers said in November they were considering a sale.
Announcing its initial bid, Sheikh Jassim’s Qatari consortium said it “plans to return the club to its former glory”.
Known as a lifelong Manchester United fan, Sheikh Jassim is the chairman of Qatari bank QIB and the son of the former prime minister of Qatar.
Ineos, owned by 70-year-old British billionaire Ratcliffe, has a history of investing in sports and owns Ligue 1 club Nice and Swiss club Lausanne.
Its sports portfolio also includes the high-profile INEOS Britannia sailing team, led by Sir Ben Ainsley, and a five-year partnership with the Formula 1 Mercedes team, while it took over the headquarters in 2019. Great Britain’s Team Sky cycling team.
At the time of the first bid, it was understood its proposal would have emphasized that Manchester-born Ratcliffe would be the “English guardian of the club” and aim to “return Manchester to United”.