A 15-year-old boy was stabbed in the stomach at Walthamstow Central Tube station on Thursday, police said.
A fight between a group of young men started just before rush-hour at 4.30pm, according to the BBC.
The station was closed to trains after the stabbing, but was operating normally on Friday morning.
British Transport Police said in a statement:
"One of the youths, believed to be 15-years-old and from Leyton, received stab wounds to side of his stomach and was taken to a London hospital, where he remains. His condition is described as stable and his injuries are not believed to be life-threatening."
Police said a 16-year-old boy from Chingford Mount was arrested on suspicion of affray. He has since been released on police bail, officers said.
Detective Chief Inspector Hugh Borgeat, one of the investigating officers, said: “We have already made several lines of enquiry into this incident, including seizing CCTV footage in and around the area to try and piece together what took place before, during and after the attack.