A goalkeeper's water bottle was urinated in during a match, prompting police to arrest an opposition fan.
A video on social media showed a man throw a bottle on to the pitch behind the QPR goal during their match against Middlesbrough at Loftus Road on Saturday.
It is believed the bottle may have been taken earlier by a pitch invader.
The Metropolitan Police said a man was charged with throwing an item on to the pitch and will face court.
