Officers are investigating after a man’s fingertip was posted through a letterbox in Bognor Regis, a Sussex Police spokesman confirmed.
The incident was reported to police on Tuesday, September 10.
Police are attempting to establish who the fingertip belongs to, but have not yet been able to identify the casualty.
Enquiries have been made at hospitals and CCTV in the area has been checked, police said.
Police have confirmed that the fingertip belongs to a man and a DNA profile has been obtained.
The profile has been checked against the national DNA and Missing Persons databases – but with a negative result, police said.
The investigation continues.
Chief Inspector Jon Carter, Chichester and Arun District Commander, said: “This is an unusual and isolated incident.
“While we accept it may be alarming, I would like to reassure people that there have been no reports of similar incidents in the area, and at this time, there is no evidence to suggest that this is part of criminal activity, or that any person has been targeted.
“If anyone does have information that may assist this investigation, I would ask them to call Sussex Police quoting reference 1170 of 10/09.“