A policeman has been arrested by detectives investigating the awarding of Police Service of Northern Ireland vehicle contracts.
He was among six men detained in England and Northern Ireland on suspicion of a range of offences including bribery, misconduct in public office and procuring misconduct in public office.
Those arrested in Antrim, Down and Tyrone included the 48-year-old officer, a 37-year-old member of police staff, a former officer aged 54, and a 62-year-old civilian, police said.
Two members of the public apprehended in England are aged 34 and 54.
A PSNI spokesman said: "The police service expects its officers and staff to behave professionally, ethically and with the utmost integrity at all times.
"Any conduct which brings or is likely to bring discredit on the service will be investigated to establish whether or not a breach of the code of ethics has occurred. This may, as a result, lead to a criminal investigation."
The suspects have been taken to Antrim Police Station for questioning.
Homes and businesses were searched and items seized.