There was disruption across the line this morning (December 17) after reports of a fight involving three young men involving knives at 10.30am.
Medics treated a man, in his 20s, at the scene for a head injury after being stabbed and he was taken to hospital.
Colliers Wood station has been shut since the attack, and at the time of reporting it has been over four hours with no sign of when it will reopen.
At the scene, the station has taped off with barriers set up to refuse the public entry.
Officers are also standing by the entrances too.
There were initially severe delays and later minor delays across the Northern line due to the incident.
Service has since returned to normal, but Colliers Wood station remains closed as police investigate.
Before being taken to hospital, the man was arrested at the scene by police on suspicion of possessing an offensive weapon.
His injuries have since been assessed to not be life-threatening or life-changing.
One eyewitness said: “The knife fell onto the track which the police have. The two guys ran away.”
“People were really shook up,” he added, “It was brutal, absolutely brutal.”
Enquiries are ongoing, and anyone who has information or witnessed the incident is asked to contact BTP by texting 61016 or by calling 0800 40 50 40, quoting reference 211 of 17 December.
