British police were holding a 53-year-old man on Tuesday over a collision that turned a joyous soccer celebration in Liverpool to tragedy and sent more than two dozen people to hospitals, four of them in very serious condition.
Police said they are not treating the incident as terrorism and are not looking for other suspects.
Detectives were working to piece together how a minivan plowed into crowds packing a narrow street, just after the players of Liverpool Football Club celebrated the Premier League championship with an open-topped bus parade.
Water Street, near the River Mersey in the heart of the city, was cordoned off by police tape, and a blue tent had been erected on the road strewn with cans and bottles.
Liverpool City Metro Mayor Steve Rotheram said four of the injured were "very, very ill in hospital."