One suggestion was it planned to bid for a well-known US oil group.
Enterprise is known to be on the takeover trail and rumours have linked it with a number of oil groups in recent months.
Jarvis, the construction group which has moved into railway maintenance, has confirmed it has another major deal in its sights.
It is involved in talks to form a joint venture with Relayfast, which looks after 6,000 miles of track.
Its main customer is Railtrack.
Jarvis advanced 9p to 286.5p; two years ago the price was just 4.75p.Reuse content