This tweet, believed to be from a 17-year-old Liverpool fan, allegedly targeted Newcastle United defender James Perch after the two sides met on Sunday.
A call about the abuse James Perch allegedly received was made to Northumbria Police, but because the complainant was from County Durham, officers from that force will take up the issue.
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A man, reportedly armed with a knife and a baseball bat, has been detained close to the event.
A remarkably mild night
Thousands of people have gathered in the centre of Manchester for a vigil in the wake of the terror attack.