Police are investigating after two "malicious" devices were placed on railway tracks in a "pro-Brexit" sabotage attempt.
British Transport Police confirmed the devices were found near Yaxley in Cambridgeshire on March 21 and Netherfield in Nottinghamshire on March 27.
It is believed the devices were found by Network Rail members of staff and "intended to cause disruption" to train services. Officers believe the sabotage attempts "relate to Britain's exit from the European Union".
British Transport Police confirmed the devices contained "literature relating to Brexit," prompting the link to pro-Leave campaigners.
Assistant Chief Constable Sean O'Callaghan, from British Transport Police, said: "This was a serious and deliberate attempt by someone to cause significant sabotage and disruption to Britain's rail network.
"We are urgently investigating the circumstances behind both incidents and are working extremely closely with our national partners, including the rail industry.
"It is important to highlight that these acts were intended only to delay services and not cause damage to the infrastructure, however this failed on both occasions."
"We're are currently keeping an open mind on why someone would put their life at risk to place these items on a live railway, however our early assessment has led us to believe it relates to Britain's exit from the European Union.
"We'll continue to monitor this situation extremely closely and have circulated advice to rail operators and indeed Network Rail."