Network Rail said it had been using its anti-theft device SmartWater to protect its cables for a number of months. This was in response to overnight thefts of 50 yards of copper power cable and 50 yards of telecommunications cable which halted services between Bolton and Blackburn and disabled the signalling system. The invisible fluid is sprayed on the cables and then leaves its mark on anything it comes into contact with, such as the thieves' skin or tools.