A teenager was in a critical condition in hospital on Monday after being stabbed at an underground station in London, police said.
Detectives said the 19-year-old was found with a stab wound to his abdomen at East Ham station in east London on Sunday night.
A second 19-year-old man was found nearby suffering from head injuries and is also in hospital. His condition is not life-threatening.
"At this early stage, it is believed there was an altercation in a street near to the underground station, resulting in the two men being injured. The circumstances of that altercation are not yet known," police said.
The incident was just a day after young actor Robert Knox became the 14th teenager to be murdered in the capital this year, once again propelling the issue of youth violence to the top of the political agenda.
Knox, 18, was stabbed to death during a "large disturbance" outside the Metro Bar on Station Road, Sidcup, Kent, in the early hours of Saturday morning. Three other men were also left with serious knife wounds.
"With knives there are no winners and only losers. If you are a person who carries a knife, think about the consequences before you carry the knife," said Knox's father Colin, 55.
"If you carry a knife there's the intention to use it, so please don't do that for the sake of my son."
The teenager had a small part in the forthcoming film Harry Potter and the Half-Blood Prince, and a stream of messages have been left by his friends on websites with bunches of flowers left outside the bar where he was killed.
Detectives are still questioning a 21-year-old man arrested on suspicion of Knox's murder.
In response to the incident, Police Minister Tony McNulty said the government had done "much of what we can in terms of legislation" and said there would be "no knee-jerk reaction".
"The stark message for young people needs to be, starkly you will end up either dead or in jail if you persist in carrying a weapon," he told Sky News.
Last week, Home Secretary Jacqui Smith promised extra money to help tackle gang violence, particularly knife and gun crimes.
Part of the cash will be used to help police carry out increased stop and search campaigns to target young people suspected of carrying weapons.