LONDON (AP) — Passengers faced significant travel disruption Saturday in Britain as a number of high-speed trains were taken out of service to undergo precautionary checks for cracks.

Network Rail, which runs the nation's tracks, said cracks were discovered on several Hitachi 800 trains. The trains are used by several train operators, including Great Western Railway, which serves passengers between London and the west of England and south Wales, and London North Eastern Railway, which connects links Edinburgh and London.

“There’s a crack that’s been spotted, and as a result of that — as a precaution — we’re checking all the trains, and while that’s taking place it’s better that they’re not used," a spokesperson for the network said.

It was unclear specifically where the cracks were found and whether the inspections will also interfere with train services on Sunday. High-speed train services between cities were affected, but suburban rail routes were still running.

Hitachi Rail has apologized for the disruption caused.

“We are working with all partners to resolve this issue as quickly and safely as possible," a spokesperson said. “We would like to offer our sincerest apologies to passengers for the impact this may be causing for their travel plans.”

Manuel Cortes, general secretary of the Transport Salaried Staffs Association, said the trains “must not be allowed back into service until we are 100% certain these trains are safe.” He said passengers should not be charged extra in the future to cover the cost of any needed repairs.