Five people are being questioned after an undercover police officer was shot in the shoulder during a surveillance operation in east London.
Armed police were at the scene after the officer was shot
The officer, who is in his 40s, was with a colleague from the Violent Crime Directorate when he was shot in Leyton on Tuesday afternoon.
Both men had been in plain clothes and were not armed, Scotland Yard said. The injured man is in a stable condition.
Two men were arrested at the scene and a further three were later arrested.
All five men are being held in police custody in different east London police stations.
A spokesman said they were not yet in a position to discuss the "fuller circumstances" of the shooting.
Later a spokeswoman said several other people were thought to be involved and police were hunting them.
London Ambulance Service said they received a call at 1540 BST to Chichester Road in Leyton. The two arrests are thought to have been made nearby in Oakland Road.
People living in the area were surprised at the unfolding events.
One woman, 34, who did not wish to be named, said: "I was in the garden, listening to the birdsong, thinking how nice and quiet it is living in Leytonstone.
"That's when I heard a gunshot go off."
She described seeing a man running down the road, apparently limping, shortly before police and ambulances arrived.
Resident Matthew Coe, 36, said: "I was going round the corner, just getting some shopping. There was a car chase and the cops said a police officer had been shot."
Brian Flint, who lives in Chichester Road, said he heard a shot while painting in his back garden.
"There has been a great deal of police activity, knocking on the doors, interviewing people, trying to find out as much information as they can," he said.