Rail passengers experienced 20-hour delays last week after telephone cable was deliberately thrown onto lines near Peterborough.
The disruption is estimated to have cost Network Rail £90,000 in compensation to inconvenienced train companies.
Eighty-five trains were affected by the delays, with five services being cancelled as a result.
Pc Christopher Thompson-Chambers said: “A train driver traveling through the area at around 8.30am reported cable, five metres in length, was thrown off Mayors Walk bridge directly onto the lines.
“There was a loud bang and bright sparks which followed as trains were brought to an immediate halt.”
PC Thompson-Chambers added: “This was mindless damage which caused delays to services heading into the city all morning and into the afternoon.”
Vicki Beadle, community safety manager for Network Rail, said: “Actions like these are reckless and irresponsible”
“Passengers suffered considerable disruption and the resulting compensation is money which would have been better spent improving the railway.”
If anyone has any information about the incident they are being urged to contact British Transport Police (BTP).
