More than 70 metres of cable has been cut from a railway near Bury St Edmunds.
British Transport Police (BFP) were called to the incident close to Elmswell station at 10.15am on Wednesday, after engineers working on the line discovered damage.
A full area search was carried out by BTP and Suffolk Police, who discovered long lengths of cable had been cut and disturbed, although not taken.
A grey Mitsubishi Shogun had been abandoned close to the scene on Monday, which detectives believe the offenders used to access the line.
No delays were caused to trains running through the area and the cable was removed by Network Rail engineers to be repaired.
BTP is now appealing for anyone who may have seen suspicious activity in the area, or who may have seen a similar vehicle close to the tracks, to come forward.
Anyone with information should call BTP on 0800 405040 quoting incident number 148 of 30/10/2013.
Information can also be passed to Crimestoppers, anonymously, on 0800 555111.