Supt Stephen Swales, district commander of Middlesbrough, said most of the away fans enjoyed the build-up to the match by relaxing in the city's pavement cafes and mixing well with locals.
'Known risk'
But around 25 Swiss hooligans tried to confront a larger group of English supporters, until police intervened.
Then, just before the match, around 30-35 local thugs attacked Middlesbrough supporters drinking in a bar outside the stadium, and turned over chairs and tables.
Riot police fired baton rounds and tear gas to retain order, although water canon remained on stand-by.
A small group of "known-risk" 'Boro fans then sought out Swiss supporters and a brief fight took place, although no-one was arrested.
Mr Swales said: "There was increased tension before the game but the match passed off peacefully.
"Ninety-nine per cent of Middlesbrough supporters showed great restraint and caused no problems whatsoever."