Five men arrested for questioning about the murder of PSNI Constable Ronan Kerr last April have been released without charge.
A 22-year-old man from Coalisland was released this afternoon.
Four other men who had been detained were released tonight.
A 23-year-old woman who was arrested today in Omagh, Co Tyrone, remains in custody.
She is being questioned at Antrim Police Station.
Sinn Féin Deputy First Minister Martin McGuinness has criticised the police operation, saying it would not help bring Constable Kerr’s killers to justice.
Mr McGuinness had particular criticism for the arrest of the 22-year-old man.
Mr McGuinness said there was no way the individual in question could have been involved in Constable Kerr’s murder and added that the arrest cast doubt on the quality of the investigation.
In a statement, Mr McGuinness said: ‘I know the family of the young man arrested yesterday in Coalisland. It was claimed by the PSNI that the arrest and search operation at his family home was in connection with the murder of Ronan Kerr'.
'The young man who was arrested and subsequently released today was in the USA at the time of that murder and was in no way involved in it,' Mr McGuinness said.
Mr McGuinness added that he has been in contact with the PSNI to register his dissatisfaction at the operation.
Constable Kerr, 25, a Catholic member of the PSNI, was killed when a booby-trap bomb exploded under his car outside his home in Omagh on 2 April.
The officer in charge of the investigation, Detective Superintendent Raymond Murray, said police were determined to pursue every possible line of inquiry.
A £50,000 reward remains on offer for information leading to the arrest and conviction of those responsible for Constable Kerr's murder.
