Thousands of commuters were trapped on trains across Merseyside for more than an hour after signal failure halted services across the local rail network. About 40 trains, each containing up to 200 passengers, were unable to move when contractors cut a signal cable at the control centre at 08:50 BST. Some passengers on trains between Liverpool and Wirral were left stranded in tunnels beneath the River Mersey. Merseyrail said services were now running again but subject to delays. Several trains which were trapped in tunnels under the Mersey for about an hour were eventually returned to stations on either side of the river. A spokeswoman for Merseyrail said the fault occurred when a contractor cut through a cable at the network control centre in Sandhills, north Liverpool. She said: "We would like to apologise to all our customers that have suffered significant delay to their journeys as a consequence of this morning's events. "Initial investigations indicate the cause of the incident was damage to key signalling equipment as a result of actions by Network Rail, resulting in all power to signalling across the entire network being lost." A Network Rail spokesman said: "Early indications are that the fault was caused by damage to cables whilst work was being undertaken for Network Rail in an electrical relay room. "Repairs have been carried out and systems and services are returning to normal. "We apologise for any disruption Merseyrail passengers may have experienced this morning." Merseyrail operates on a 75-mile network across the Merseyside region, with lines travelling between Liverpool and Southport, Ormskirk, Kirkby, Hunts Cross, New Brighton, West Kirby, Chester and Ellesmere Port. It includes five underground stations - four in Liverpool city centre and one in Birkenhead. Merseyrail runs almost 800 trains a day, which carry an average of 100,000 passengers.