A group of three boys and one girl, in their late teens, stabbed a plain clothes police officer in east London last night, Scotland Yard said.
The officer was today in a non-life threatening condition in hospital after being stabbed near a pub in Bow.
It was reported that at least one arrest has been made.
The incident prompting a huge response from the Metropolitan Police on Tuesday night with Tower Hamlets police tweeting to advise the public to stay away from the area.
Nearby residents tweeted pictures of the ongoing forensics operation last night.
London Air Ambulance and London Ambulance Service treated the injured officer who was taken to a nearby hospital in a non-life-threatening condition.
A man was arrested on suspicion of attempting to murder the officer, after he was attacked near the Bows Bell Pub on Bow Road at 9.22pm on Tuesday.
Scotland Yard said the incident was not being treated as terrorism related at this stage and a knife was recovered, the Press Association reported.