But all the firms said that they had no interest in Peterhouse, or were not thought to be in a position to make a bid.
Stephen Rawlinson, an analyst at Arbuthnot, said that this indicated that an overseas firm was the likely buyer. He said: "You cannot rule out one of the overseas players, maybe even an American outfit."
A leading City analyst added that a possible contender was the American firm Jacobs Engineering. Last year, a Jacobs subsidiary won a Network Rail design contract and some believe the firm might use the rail expertise at Peterhouse to built on its breakthrough in the British market.
UK firms are believed to have been put off by recent problems at Peterhouse.
A possible contender is American firm Jacobs Engineering, which could look at Peterhouse as a way of expanding rail work
Its lucrative rail maintenance contracts were taken in house by Network Rail at the end of last year, eating heavily into profit.
However, Peterhouse is expected to receive compensation from Network Rail, as well as payment for some of its rail equipment and some small short-term maintenance contracts.
Some of the City speculation has, however, been knocked on the head. The options that appear to have been ruled out include: n A break-up of the company. Source close to Peterhouse said that this had not come up in initial sale talks.