Former chairman Ron Greenhalgh and former chief executive Ken Fox launched their bid for the £160m-turnover business after it recorded a £13m loss last month. It is understood that Kier may be another interested party.
Allen finance director Neil O'Brien said the board would choose between the three bids by mid-April. O'Brien said: "We've had a number of proposals. These are all being progressed over a reasonably short time." Analysts believe that Greenhalgh and Fox are favourites to buy the business. One said: "There may be others wanting a look and plenty will get the sale memorandum. But Ken and Ron are in pole position because they know it. Although whether they get it, that's another question." The construction sale is part of a restructuring plan under which Allen will focus on equipment hire and be renamed Speedy Hire.
Allen said last month it would have to put more money into the struggling division to attract buyers.
O'Brien denied City rumours that the group had run into problems over the sale of its utilities division, Ryan. He said more than 10 companies had expressed an interest in buying the business, but that its sale would not be completed until the construction deal was sealed.
However, one source said disputes with a major client made Ryan's contracts practically worthless and there was no sign this problem would be resolved in the near future.
The source said: "Allen can't sell it because it hasn't got it sorted. The contracts are worthless because to fulfil them will cost it money. Nobody will buy it like that." The source said Allen would probably be forced to accept less than it hoped for Ryan.
O'Brien insisted that any problems with the contract would be resolved in the next few weeks and would not delay the sale.
Last week, Allen announced that it had sold G Pearce Civil Engineering for a loss. Rifsons Venture Capital bought the Wiltshire-based civil engineering firm for £188,000.