A man has been arrested in Derry in connection with a claim of responsibility by the New IRA for the shooting of senior detective John Caldwell.
It comes after a typed message was posted on a wall in the city purportedly from the New IRA and claiming responsibility for Mr Caldwell's attempted murder.
Police have said the New IRA is the main line of inquiry in the investigation.
The detective remains critically ill in hospital after being shot several times at a sports complex in Omagh last month.
A PSNI spokesperson said: "Detectives investigating the attempted murder of Detective Chief Inspector John Caldwell on February 22 have arrested a man in connection with the claim of responsibility following the attack.
"The man was arrested under Section 41 of the Terrorism Act 2000.
"He was arrested this morning, Saturday March 18, following the search of a property in Derry.
"He has been taken to Musgrave Serious Crime Suite for questioning."