Three people taken into custody after a 14-year-old boy’s arrest sparked protests outside a police station have been released under investigation.
The boy was held on suspicion of possessing cannabis in Colindale, north-west London, on Friday.
Two men were arrested on suspicion of obstructing an officer as the police vehicle left the scene of the arrest.
About 40 people then assembled outside Colindale Police Station in Barnet, where one protester was arrested.
All four have since been released under investigation.
Scotland Yard said they had been carrying out a “routine patrol” in The Concourse at about 14:00 BST when the 14-year-old was searched and arrested.
Two men, aged 23 and 25, were then held as crowds gathered and “obstructed the police vehicle from leaving the scene”, the Met said.
A youth worker from charity the 4Front Project tweeted that he and another colleague had been arrested “for doing our jobs”.
After the police vehicle left, protesters made their way to the police station and “a number of officers received minor injuries” as they tried to disperse the crowd.
The protester, a 19-year-old man, was arrested on suspicion of assaulting a police officer.
The Met said they had “not received any reports that members of the public or those under arrest sustained any injuries”.
Ch Supt Roy Smith said: “Even when well-intentioned, interfering or obstructing officers carrying out their lawful duties can cause far more problems than it solves.
“I am committed to listening, learning and improving but my officers must also have the ability to carry out their duties safely and without fear or favour.”
He added the 14-year-old’s arrest “was not as a result of a raid or anything of that nature” and 13 bags containing cannabis had been found during a search of the area.