A statement from the Police Service of Northern Ireland said:
Detectives from the PSNI's Serious Crime Branch, with assistance from officers in Cumbria Constabulary and the North West Counter Terrorism Unit, are conducting a number of searches in Northern Ireland and north west England.
The search activity is in connection with the wider investigation into the murder of PSNI Constable Ronan Kerr in April 2011 and linked incidents.
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The 12.5 hour walkout by 63 GMB members got under way at 6am this morning and will continue until 6.30pm this evening.
37-year-old Graeme Haddon pleaded guilty to the offence which happened in his home village of Lamancha near West Linton at the weekend.
Laura Price was dragged into an alleyway, close to Penrith Leisure Centre, where she had her head jumped on and kicked "like a football".