"It is nonsense to say that Gwenog [Jones] wanted the Holyhead fans to riot. Yes, maybe she did say that Wilda [Griffiths] deserved to be gnawed to death by starving tarantulas, but that was a light-hearted remark."
-- a Holyhead Harpies representative (DP4)
Ministry fears of violence at the match between traditional rivals Holyhead Harpies and Puddlemere United were realised when former Harpy, Chaser Wilda Griffiths, disappeared midway during the match. Many Puddlemere and Holyhead supporters had handed in “dummy” wands at the gates and used their real wands during the ensuing riot. Holyhead team captain Gwenog Jones is said to be “helping the Ministry with its enquiries” (DP4).
If someone is "helping the police with their enquiries" it is taken to mean they are being held in custody while the police gather enough evidence to press charges....
Although the date printed on the fourth Daily Prophet Newsletter (DP4) is 1 October 1999, the timeframe for this event is 1992-1993.
From the Web
Writing by J K Rowling on Pottermore: The Daily Prophet