While police completed their search of "up to 20" planters that McArthur was known to use weeks ago, it only recently became evident that remains of a seventh person were among those previously discovered.
Police have so far identified three sets of remains they found in large planters at a home where McArthur did gardening work and rented storage space - those of Andrew Kinsman, 49, Soroush Mahmudi, 50, and Skandaraj Navaratnam, 40. The remains have not been identified, and Idsinga made it clear they have not been linked to the unidentified man in the photograph.
Only three of the seven sets of remains have been identified.
McArthur was first charged in January in connection with the murders of Kinsman and Esen, who disappeared from the Church-Wellesley Village in 2017.
Bruce McArthur, a 66-year-old freelance landscaper who was accused by Toronto police January 29, 2018 of murdering five people and putting their dead bodies in large planters on his clients' properties, appears in a photo posted on his social media account.
Detective Sgt. Hank Idsinga said Monday they could not identify the man in the picture and are now seeking the public's help.
"As I have stated before, these remains are of individuals who have been dismembered", said Idsinga.
McArthur, a grandfather and former mall Santa Claus, has not been charged with a seventh count of murder related to the unnamed victim's death.
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Idsinga said they showed the picture to members of the gay community but could not identify him.
While Idsinga has an idea of how at least some of McArthur's alleged victims were killed, he said investigators have been unable to definitively determine the cause of death in each case.
The Mallory Crescent property where the self-employed landscaper worked and stored his tools has been ground zero for the investigation, with at least six other sets of remains found in planters there. They are Selim Esen, 44, Majeed Kayhan, 58, and Dean Lisowick, 43 or 44.
Chief Forensic Pathologist for the Province of Ontario Dr. Michael Pollanen was also on hand at the news conference.
Detectives are looking at numerous unsolved missing persons cases in the area to see if they could be connected to McArthur.
McArthur's next court hearing is set for March 14.
Edward Royle, a lawyer for McArthur, has previously declined to comment on the case and didn't respond to a message seeking comment on Monday.
Police said there was still much more to do.
The earliest murder charge laid against McArthur dates back to 2010, sparking questions as to how his alleged actions escaped notice for years. As per his sentence, McArthur was ordered to stay away from the part of Toronto that included the Gay Village.