Police have rushed in force to Letchworth railway station after an alleged robbery at a town centre cashpoint.
Officers including a dog unit and a police helicopter are in the area of the station searching for the thief.
The male suspect is said to have stolen money from another man at a Leys Avenue cashpoint at 10.20am before running off towards the station.
Witnesses have described more than 10 police cars rushing to the scene along Station Road, with trains stopped northbound as officers go through carriages to search for the alleged thief.
A man is also alleged to have trespassed on the railway lines at Letchworth.
Line operator Great Northern has confirmed that all lines have reopened, though services between Hitchin and Cambridge may still be subject to cancellation.
Greater Anglia have tweeted that following the Letchworth incident they will be accepting Great Northern tickets between Liverpool Street and Cambridge.
No arrests have been made so far.
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