Counter-terrorist units are investigating an attack on two prison officers at Full Sutton maximum security jail near York.
One warder was held hostage for several hours by three inmates.
The Prison Service has stressed that they were not serving sentences for terror-related offences.
The attack comes less than a week after the murder of Drummer Lee Rigby in Woolwich.
Gregg Easteal reports.
More top news
Kerrie Gosney brings you Saturday night's forecast
Showers becoming heavy and thundery Saturday afternoon. Drier for a large part of Sunday
Robert Hodgson, from Stanley, County Durham, committed the offences on the girls, aged as young as five or six, up to the age of 13.