A homicide investigation has been launched after a man's body was found in a Levin park last week.

Police were notified at around 5.40pm on Thursday after the man's body was found in a building at Muaūpoko Park, near Lake Horowhenua.

The death was originally treated as suspicious and following a postmortem and scene examination which were completed yesterday, police have launched a homicide investigation.

"Members of the deceased's family and Muaūpoko iwi were present at the conclusion of the scene examination, where a karakia was performed," Detective Senior Sergeant David Thompson said.

A rāhui has been placed on the Lake Domain by Muaūpoko, which is supported by both the Lake Trust and Lake Domain Board.

"The rāhui will remain in place until further notice."

Investigators would like to hear from anyone who was in the lake area on Wednesday, October 16, and Thursday, October 17.

"This includes any vehicles or people seen in the area around the old Rowing Club and Sea Cadets buildings over those two days."

Police also want to see any dashcam footage from people who were in the Lake Domain area on Wednesday and Thursday.

"The area is a popular spot for members of the public to drive or walk through."

Anyone with information is being asked to call police on 105 or Crime Stoppers anonymously on 0800 555 111.