Video report by Gregg Easteal
Rail services on London North Eastern Railway (LNER) are being disrupted for a third day due to cracks in trains.
LNER is running a reduced service on the East Coast Main Line, which runs between London King's Cross and Edinburgh via Peterborough, York and Newcastle.
The operators' Hitachi Class 800 trains, known as Azuma trains, were withdrawn from service on Saturday for safety checks after cracks were discovered in part of the chassis of some trains.
LNER posted a message on Twitter stating the issue is "likely to be going on for a number of weeks".
A spokesman for the operator said: "LNER is working with Hitachi and other the rail industry partners to return as many trains back into service as safely and as quickly as possible.
"As investigations are continuing and the schedule for repairs is being developed, further information on timings will be released in due course."
Robert Nisbet, director of nations and regions at industry body the Rail Delivery Group, said if inspected trains are found to have "tiny cracks" then replacement trains may be deployed while repairs are carried out.
Asked if he knows how long the disruption is likely to last, he told BBC Radio 4's Today programme: "No, I can't put an exact time on it and that is purely because we are going through the process and taking it extremely seriously."
Mr Nisbet described the disruption as "disappointing" because more passengers are returning to using the train network following the easing of coronavirus restrictions.
In response to a question on how long trains have been running with cracks, he said: "These trains are relatively new in service, so this is something that the Hitachi engineers will be looking at and reporting back to the train operating companies."
On Sunday he said that the cracks - measuring millimetres - are on the "lifting points on the underside of the carriages used for maintenance".
He added that this "didn't pose any particular danger to passengers" but they "have the potential to develop" if left untreated.
Rail minister Chris Heaton-Harris asked Hitachi - which builds and maintains the Class 800 trains - to identify to extent of the cracking and "whether carriages can still run safely" despite the issue, the Department for Transport said.
He also urged the industry to manage capacity by using "alternative trains" on the affected routes and delivering a "clear rail replacement schedule" using buses and coaches.
Hitachi apologised to passengers and train companies, adding that some trains have returned to service after being checked.