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Detective Senior Sergeant Colin Blackie said about 15 people, including police officers from Oamaru, Dunedin and Central Otago, police forensic experts and two ESR scientists, were working on the case.
The group was working to establish the movements of the man and how he died.
The body of the Oamaru resident was discovered last night at commercial premises in a block of shops at the corner of Arun and Hull Sts.
A scene examination is under way. The priority was getting the body to Christchurch for a post mortem, Det Snr Sgt Blackie said.
The man's identity would not be released at this stage.
"Police are keeping an open mind as to how this death was caused and it is currently being investigated as an unexplained death," he said.
An investigator had been appointed to specifically care for and liaise with the next of kin, and the victim support agency had been working with the family.
Anyone with any information regarding the incident should ring police on (03) 471 5002