A former PSNI Assistant Chief Constable, Duncan McCausland, has been released pending a report after he was arrested in connection with an investigation into the awarding of contracts for PSNI vehicles.
A police staff member has also been suspended after he was arrested as part of the investigation.
The 37-year-old has now been released, pending a report to the Public Prosecution Service.
He, along with the former high-ranking police officer and serving officer, are among seven people who have been arrested on connection with the investigation.
Four people were arrested in Northern Ireland, including a 48-year-old serving police officer, 62-year-old civilian and the 37-year-old PSNI staff member - now suspended.
A former Assistant Chief Constable - Duncan McCausland (54) was also detained on Tuesday.
He has now been released pending a report to the Public Prosecution Service.
Two other men – both civilians, aged 34 and 54 – were detained in England and transported to Northern Ireland.
The men were arrested on suspicion of a range of offences including bribery, misconduct in public office and procuring misconduct in public office.
Searches were carried out at houses and businesses following the arrests in counties Antrim, Down and Tyrone.
On Wednesday, a seventh man, aged 71, was arrested by police. He remains in police custody.