Football thugs clash at Port Vale's Vale Park stadium
Trouble flared just two minutes into the game when a a smoke bomb was thrown into the home end by visiting Blades supporters at Vale Park.
A group of Port Vale fans then tried to storm the away stand with unconfirmed reports suggesting a youngster was hit by the missile.
Stewards battle to keep rival fans apart
It became apparent there were groups of people intent on being involved in disorder
Superintendent Carl Ratcliffe
Staffordshire Police Commander Superintendent Carl Ratcliffe said: “It became apparent there were groups of people intent on being involved in disorder.
“Our priority was to ensure we disrupted the intentions of a minority with their minds set on causing trouble.”
Violence flared when away fans threw a smoke bomb into the home stand
Port Vale Supporters’ club vice chairman Mark Porter said: “People should not be throwing flares, somebody could get seriously injured.
"People should think about their actions as they could have grave consequences and seriously hurt somebody.
"I think when there is trouble it ruins the day and what should be a game of football."
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Thousands of fans flocked from Sheffield to Stoke-on-Trent to celebrate Chris Wilder’s side’s promotion back to the Championship after a six-year exile.
The crowd violence marred United’s 3-0 win over struggling Port Vale.