Transport police are appealing for help in catching thieves who stole two separate lengths of copper cable from railway lines in the North West.
Passengers travelling between Manchester and Clitheroe suffered severe disruption on Thursday after the cables were taken the night before.
Network Rail said the thefts, near Hall i'th' Wood station, meant normal service was not resumed until 1630 GMT.
Anyone with information is being urged to contact police or Crimestoppers.
Network Rail said it was using anti-theft device SmartWater to protect its cables, and had been doing so in the region since November.
Stranded at stations
The invisible fluid is sprayed on the cables and then leaves its unique signature on anything it comes into contact with, such as the thieves' skin or tools.
Det Insp Andrea Rainey said: "BTP (British Transport Police) takes cable theft extremely seriously and we fully investigate every incident.
"It is not, as some people think, a victimless crime or one that just affects the rail industry; the knock-on effects of the thefts have a far-reaching impact.
"Countless people are left stranded at stations whilst repairs to the line are carried out, which results in lost work hours for other businesses and severe disruption for commuters.
"We have specialist officers who deal solely with cable theft and they will utilise their expertise to investigate this latest incident."