There have been a number of serious stabbings and other violent incidents at the Notting Hill Carnival, police have said.
A Section 60 order was imposed in and around the area of the carnival at 9.24pm and will last until 1am.
It allows a police officer to stop and search someone without suspicion.
It comes on the final day of the west London carnival, which has been enjoying its first year back since the pandemic.
Close to a million people were at the event for Adults Day on Monday, as the streets were once again filled with the boom of sound systems and dancers in extravagant costumes.
Police earlier said there had been 76 arrests for "a variety of different offences" by 7am on Monday.
A police horse also died on duty during after collapsing at around 9pm on Sunday.
There were 72 seconds of silence on Monday afternoon to mark the 72 people killed in the fire at nearby Grenfell Tower - one of several gestures held over the weekend to remember the tragedy.
Notting Hill Carnival celebrates Caribbean culture and is Europe's biggest street party, and second only in size to the carnival in Rio de Janeiro in Brazil.
The 2020 carnival was cancelled because of COVID, although there were live-streamed events, and last year's event was also scrapped due to coronavirus risk.