Two men have been taken to hospital after a hammer attack at Stratford station in east London during the morning rush-hour.
British Transport Police officers were called to the station shortly before 6am on Monday morning, after reports of an assault.
A witness claimed on Twitter that one man was struck over the head with a hammer after being refused a cigarette.
In a statement, BTP said one victim suffered "a laceration to his head as well as a suspected fracture shoulder" during the attack, while another victim was being treated for "minor bruising".
The two men's injuries were described as non life-threatening.
Arrested on suspicion of common assault
A 26-year-old man, from East Ham, was arrested on suspicion of actual bodily harm, common assault and possession of an offensive weapon.
Police confirmed that a hammer was recovered from the scene during his arrest and that the suspect remains in custody.
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A BTP spokesman added: "Inquiries are now under way to understand exactly what happened in the moments leading to both men being assaulted."
Witnesses to the incident are asked to contact BTP by sending a text to 61016 or by calling 0800 40 50 40 quoting reference 49 of 30/10/2018.
Alternatively, witnesses can call Crimestoppers anonymously on 0800 555 111.