Police were called to a private address in Wootton Hall Park shortly after 1pm today (Thursday) and arrested a 49-year-old man who is a serving officer with Northamptonshire Police.
He has been taken into custody and is due to be questioned by detectives
A post mortem investigation will be carried out later by a Home Office pathologist in Leicester.
A police spokesman said the overall investigation will be led by the East Midlands Special Operations Unit, headed by Det Supt Kate Meynell.
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It will be carried out by officers, including scenes of crime specialists, drafted in from across the region, but will not include anyone from Northamptonshire Police.
Det Supt Meynell said: “A full and proper investigation is taking place. Northamptonshire Police will not be making any further comment on this investigation at this stage.”
The incident has been referred to the Independent Police Complaints Commission.
Anyone with any information can call Northamptonshire Police on 101. Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111 or use the anonymous online form at www.crimestoppers-uk.org.