Train passengers are facing cancellations and delays due to a points failure between Diss and Norwich.
Greater Anglia said that the points failure, on Bank Holiday Monday afternoon, meant some lines were blocked.
The rail company tweeted that some trains might be cancelled, delayed or revised.
Network Rail engineers are on their way to the location of the problem.
Greater Anglia said services departing from Norwich may be delayed, with some starting and terminating at Diss, while trains heading from Diss to Norwich were unable to get into Norwich Railway Station.
The 2pm and 3pm services from Norwich to London Liverpool Street were cancelled.
Points are movable sections of track which allow trains to move from one line to another.
Points can fail for a variety of reasons. They may become clogged with debris or ice, the drive mechanism may fail or in hot weather they may expand too much.
When points do fail, the system goes into 'fail safe' mode: the last signal before the set of points affected will automatically turn red so no trains can pass.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here