Trains have been delayed at one of Manchester's main railway stations after workers left platforms when a customer threatened staff.
Northern said workers withdrew from the concourse at Victoria "for a short period" at about 17:00 GMT.
Services were delayed up to 30 minutes with others cancelled and disruption is expected until the end of the day, according to Network Rail.
British Transport Police is investigating.
Chris McKeon, of the Local Democracy Reporting Service, said he was on a train to Liverpool when he heard an announcement about "a threat of serious assault against a member of staff".
"The driver said we were waiting for a despatcher and they've all walked out," he said.
"He said earlier one staff was abused and he walked out and there was another incident just before we got on the train and they all walked out."
It led to issues relating to platform allocation for trains, Northern said.