London Euston station was closed on Saturday afternoon after reports of a brawl as armed police were scrambled to the scene.
Witnesses said they saw passengers "running in panic" as the station was evacuated.
British Transport Police said: "Officers were called to Euston station at 1:27pm following reports of an altercation between two men involving the use of a knife.
"Our investigation found that there was no knife involved and no stabbing took place. The incident has been classed as ABH assault."
The station is understood to have reopened.
One woman tweeted: "Got off the train at London Euston and went down the escalator to the underground.
"As soon as I reached the gate, security closed it off."
Another Twitter user said: "What was the panic at euston underground just now about?
"Saw people running up escalators and armed police heading towards it #euston."
A spokesperson for Transport for London confirmed Euston bus station had been closed due to a "police incident."
It said: "Buses serving Euston are being diverted or [will] terminate earlier than usual.
"Please speak to the driver before boarding."
