The 50-year-old man was arrested under Section 41 of the Terrorism Act on Tuesday, November 22, in the Strabane area.
He has been taken to the Serious Crime Suite at Musgrave Police Station, where he remains at this time.
A 38-year-old man arrested on Monday, November 21, as part of the same investigation, has been released following questioning.
Four men, aged 38, 36, 36, and 28, who were previously arrested, have also been released following questioning.
Meanwhile, TIU detectives investigating the murder bid the two police officers conducted a search at a property in the Sion Mills area yesterday evening, Tuesday, November 22.
A number of items were seized and taken away for further forensic examination.