A female has been arrested in connection with the murder of policeman Ronan Kerr, who died after a bomb was placed under his car by dissident republicans on April 2.
The 23-year-old woman joins five other male suspects, who have already been questioned as part of the ongoing investigation.
The five men were detained on Tuesday and the woman was arrested in Omagh on Wednesday morning. They were arrested under the Terrorism Act and are being held at the Serious Crime Suite at Antrim police station.
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Investigators carried out searches in County Tyrone; Antrim and South Derry relating to the inquiry.
Constable Kerr (25) was a Catholic member of the Police Service of Northern Ireland (PSNI) died in April when an explosive device detonated under his car outside his home in Omagh, County Tyrone.