Two senior Northants Police officers are being investigated over potential gross misconduct.
The Independent Police Complaints Commission has issued notices of investigation to Deputy Chief Constable Andrew Frost and outgoing Deputy Chief Constable Martin Jelley.
The IPCC is investigating Mr Frost’s involvement in a professional standards department investigation and whether it was appropriate.
The IPCC is also investigating Mr Jelley’s conduct in relation to the delay in the referral of Mr Frost’s conduct to the IPCC.
IPCC Commissioner James Dipple-Johnstone will oversee the investigation.
In a statement, Chief Constable Adrian Lee said he was aware of the investigation but said it would be inappropriate to comment further at this stage.
He said: “As the Chief Constable for Northamptonshire I am the appropriate authority for conduct matters relating to DCC Jelley and ACC Frost.
“The force will fully co-operate with the IPCC in their investigations into these matters.
“As DCC Jelley moves to become the chief constable of Warwickshire Police the appropriate authority for his investigation will move to become the responsibility of PCC Ron Ball.”