Rail passengers are facing “significant” disruption across the network as a number of high-speed trains undergo precautionary checks after cracks were found.

Great Western Railway (GWR), Hull Trains, London North Eastern Railway (LNER) and TransPennine Express (TPE) trains of the Hitachi 800 model were taken out of service for “safety checks as a precautionary measure” on Saturday morning.

Hull Trains said that by 1.30pm on Saturday its normal services had resumed but GWR, which operates 93 Hitachi 800 trains, warned that the problem could affect Sunday services as well.

Hitachi Rail has apologised for the disruption caused by “cracks on the lifting points under the carriage of some class 800 trains” which were spotted during routine checks, and that by Saturday evening “some trains” had been cleared to run as normal.

A Hitachi Rail spokesperson said: “Safety is our number one priority and as a precaution, the decision was taken to halt the entry into service of our intercity fleets pending inspection.

“We understand the frustration caused and we would like to apologise for the inconvenience caused to passengers and operators.

“Having been cleared for service, some trains are now running again across the network.”

Rail minister Chris Heaton-Harris has asked operators to deploy extra staff to help passengers complete their journeys and access refunds.

He added: “I share the frustration of passengers who are experiencing significant disruption, and would ask people whose journeys are affected to check before travelling.”

The non-ministerial Government department responsible for regulating Britain’s railways, the Office of Rail and Road (ORR), has also said it is working to get trains back into service “as soon as safely possible”.

GWR said the cracks were detected on “more than one” Hitachi 800 train.

Asked how long the disruption will last, a GWR spokesman said: “It’s a question of how quickly the trains can be inspected – it’s highly likely that it will certainly persist through to the end of today.

“Once more inspection has been carried out we’ll have a better understanding as to whether that disruption is going to continue into tomorrow.”

The spokesman added that the issue is affecting long-distance journeys between cities, which are being refunded, but that suburban and rural GWR services are running as normal.

Meanwhile, all LNER services between Edinburgh, Newcastle, York and London have been disrupted and the provider has advised customers not to travel.

LNER tweeted: “Once trains have been checked, they will be released back into service as soon as possible. Please check before travel.”

Hull Trains said its services resumed at around 1.30pm on Saturday after half a day of cancellations.

A spokesman said: “We are pleased to confirm that, following thorough checks by Hitachi on the Hull Trains fleet of Class 800 series trains, services will now resume as normal.

“Due to the significant disruption that has taken place we expect our services to be extremely busy and we cannot guarantee that social distancing guidelines will be adhered to…

“We would like to apologise to all passengers for the impact this may have caused.”

TPE said its Nova 1 trains had been affected by the issue and customers have been advised not to travel via the Newcastle to Liverpool route, where a “significant number of services” have been cancelled.

A TPE spokesman said: “This problem is being investigated by the train manufacturer and, once trains have been checked, we hope to be able to release them back into service as soon as possible.”

Mick Lynch, general secretary of the Rail, Maritime and Transport union, said Hitachi must ensure “the highest safety standards” and “properly investigate and rectify the issues”.

Manuel Cortes, general secretary of the Transport Salaried Staffs Association, said passengers should not be charged extra in future to pay for repairs.

He said: “It’s welcome news that railway engineering staff have found these cracks before they led to an accident…

“It’s important to point out that the affected trains are relatively new, in which case the manufacturers should foot the bill for any repairs, not passengers or taxpayers.”

Anthony Smith, chief executive of independent watchdog Transport Focus, added: “Safety must always come first. However, it is very disappointing this is happening on a relatively new set of trains…

“Refunds should be quick and compensation generous. Many thousands will have their travel plans upset this weekend.”