The famous Flying Scotsman could be withdrawn from service - a week after its first passenger journey since being saved for the nation.

Bosses from the National Railway Museum in York, which bought the legendary locomotive for £2.59m earlier this year, say the engine may need a major overhaul after it broke down on Tuesday.

All passenger runs between York and Scarborough have been cancelled for the rest of the week while engineers investigate.

Andrew Scott, head of the National Railway Museum, said an overhaul of the steam engine was planned for 2006, but it was hoped the train would keep running until then.

He said: "We are acutely aware that we owe it to the public and the railway industry to only operate Flying Scotsman if it can be reliable. "Therefore, if our current investigations into the problems suggest that we cannot.

provide the reliability of service that the public has a right to expect, and that we should withdraw Flying Scotsman for that major overhaul sooner than expected, then reluctantly, we will have to do so."

Mr Scott defended the purchase of the locomotive, which was bought with donations from the public and billionaire Sir Richard Branson, together with a grant from the National Heritage Memorial Fund.

He said: "Whether or not Flying Scotsman was in peak condition would not have affected our decision to acquire it.

"It's value, which was determined within a competitive arena, is in its iconic status and within the hearts of the public, not in its mechanical status."

This week's breakdown on a level crossing near York city centre is the third set-back suffered by the locomotive since its arrival in the region.

In May, technical difficulties meant the world's most famous locomotive failed to appear at the launch of RailFest at the museum.

And again last week the train was more than an hour late leaving for its first passenger run since it was bought by the museum.