Police investigating the death of a father-of-two last seen alive on AFL grand final day have made four further arrests.

Chris Robertson, of Moana, was found deceased in a Lonsdale workshop on September 30 last year.

The 49-year-old had last been seen alive three days earlier, celebrating the AFL grand final.

His death was declared a major crime and in December, 30-year-old former Hells Angel Dylan Danaher, of Happy Valley, was charged with his murder.

But now, four others will also face court in connection with the tragedy.

Alleged murder victim Chris Robertson. Picture: supplied
Alleged murder victim Chris Robertson. Picture: supplied

Mr Robertson was last seen on AFL Grand Final day and his body was found three days later. Picture: supplied
Mr Robertson was last seen on AFL Grand Final day and his body was found three days later. Picture: supplied
The four suspects, who are set to face magistrates on Thursday, are:

• A 33-year-old woman from Happy Valley charged with two counts of assisting an offender and one count of carrying out threats or reprisals relating to persons involved in criminal investigations

• A 61-year-old man from Happy Valley, charged with two counts of assisting an offender

• A 29-year-old man from Christies Beach charged with carrying out threats or reprisals relating to persons involved in criminal investigations

• A 27-year-old man from Christies Beach, charged with carrying out threats or reprisals relating to persons involved in criminal investigations

All four were refused police bail and are expected to appear at Adelaide Magistrates Court on Thursday.

Det Supt Darren Fielke, who is leading the investigation said: “We will not hesitate to investigate offending of this nature and will vigorously pursue prosecutions against any person found to be assisting those responsible, interfering with investigations or threatening witnesses.”

Police found a grey Triton during their investigation into the alleged murder. Picture: SA Police
Police found a grey Triton during their investigation into the alleged murder. Picture: SA Police
Mr Robertson’s body was discovered in a warehouse in O’Sullivan Beach Road in Lonsdale, with post mortem examinations revealing him to have died of injuries consistent with an assault.

Early lines of police inquiry centred around a grey Triton link that Mr Robertson was believed to have been a passenger in prior that evening.

Police located the vehicle in late November, two weeks before what would prove the next potential breakthrough.

On December 11, Mr Danaher, 30, was arrested and charged with murder. He is next due to appear at Adelaide Magistrates Court on July 7.