Police have made four arrests following the stabbing of an 18-year-old man in a north-west London park.
Detectives believe the teenager was attacked just after 6pm in Montesole Playing Fields, in Pinner, on Wednesday.
The victim was taken to hospital were he remains in a critical condition.
On Sunday, two teenage, both aged 15, and two men aged 22 and 24, were arrested.
They all remain in police custody.
Metropolitan Police Commander Roy Smith, who is leading the investigation, said: “I know that local communities will have been shocked by this attack and would like to reassure them that we are not currently looking for any other suspects.
“I’m grateful to the members of the public who have come forward with information already to assist our investigation and local officers will continue to provide additional patrols in the park and surrounding area.”
The victim’s family are being supported by officers.