A homicide investigation 'Operation Angelo' has been launched by Police after a body was found in the Waikato River on Thursday.

The man whose body was recovered from the Waikato River near Ngaruawahia on Thursday evening can now be named as 52-year-old John Wirihana Isaac, of Hamilton.

"Mr Isaac was found in the water about 7pm on Thursday 18 January by members of the public who had taken their boat to the river," says Detective Senior Sergeant Ross Patterson.

"The men who located him did an outstanding job by getting Mr Isaac to the riverbank at Ngaruawahia, where a Police boat and Search and Rescue team were able to recover him."

As a result of a post-mortem examination, Police have now launched a homicide inquiry.

"To protect the investigation at this early stage, Police are not in a position to elaborate on the cause of Mr Isaac’s death," says Detective Patterson.

"We would, however, like to hear from anyone who has seen Mr Isaac in the past few days or any unusual activity near the river and any of the bridges between Hamilton and Ngaruawahia."

Anyone with information is asked to call 105, or make a report online at 105.police.govt.nz, clicking “Update Report”.

Please reference the file number 240119/8775.

Information can also be provided anonymously to CrimeStoppers by calling 0800 555 111.

"This is an incredibly distressing event for Mr Isaac’s whanau, and we are providing them with support at this time," says Detective Patterson.

"Further updates will be issued proactively."