The number of police officers injured during Notting Hill Carnival in London has jumped to 31, Metropolitan Police sources informed Geo News Tuesday.

The officers received injuries across both days on Sunday and on Monday, Metropolitan Police said on its website. Officers have also seized a number of weapons, including knives, CS spray, batons and a hammer during the two-day festival.

“The attacks on police are unacceptable. It was against our expectations,” Assistant Commissioner Martin Hewitt said.

On Monday, at least three people received minor injuries in the wake of a suspected acid attack on revellers at Notting Hill Carnival, Europe’s biggest street festival, British media outlets reported.

Ken Marsh, chairman of Met Police Federation, promised that police officers won’t be left alone for it would become difficult for them to discharge duties in such atmosphere.

He said the issue is being taken up at high level, including with the city’s mayor.