Chelsea have confirmed a knife was discovered by cleaning staff in a dressing room at the club's training ground.
The knife was found in the changing area of the complex in Cobham, Surrey, which is used by youth team players.
After an investigation, the youngsters were all questioned and warned of the consequences of knife crime, but no further action was taken as it was thought the knife was left behind by a contractor on the site.
A statement from a Chelsea spokesman said: "A knife was found on the premises at a time when only cleaning and building contractors had been on site.
"The club has determined that it did not belong to any player or staff member as the area was sealed off and we are satisfied it is not a matter of concern. The matter is closed."