Investigators have identified three sets of remains so far - 49-year-old Andrew Kinsman, 50-year-old Soroush Mahmudi and 40-year-old Skandaraj Navaratnam.
In a rare move, police also released a photograph of a man who they believe is a victim of McArthur's.
McArthur has been found guilty in six charges of murder.
The arrest of McArthur, a self-employed landscaper who sometimes worked as a mall Santa, has roiled the LGBTQ community in Toronto. He did not personally know McArthur, but he knew people who did.
"As I have stated before, these remains are of individuals who have been dismembered", said Idsinga.
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.
Over the past two months, police have searched about 30 properties in Toronto before zeroing in on the eastside residence where upwards of 20 planters were seized and two others it plans to excavate.
Prayers for victim and alleged shooter day after CMU shooting
Davis allegedly escaped from the dormitory on foot, leading to a campus lockdown and a citywide manhunt for the alleged shooter. They asked him if he was OK then had him call his parents because he wasn't acting logically, police said.
With the discovery of a seventh individual's remains, there are now the human remains of at least four other individuals yet to be identified.
McArthur was arrested and charged with the first-degree murder of Esen and Kinsman on January 18. He has not commented on the cause of death for any of the victims. "This is through teamwork because we need to utilise many different scientific disciplines - pathology, antrophology, dentistry, fingerprints, all of these different modalities are integrated together to understand what's happened".
He refused to detail where the photo was taken and stressed that it was not clear whether the most recent remains found belong to the unidentified man.
McArthur, 66, is charged with first-degree murder in their deaths, as well as the presumed deaths of 44-year-old Selim Esen; Majeed Kayhan, 58; and Dean Lisowick, either 43 or 44. -Sgt. Hank Idsinga, lead investigator in the case.
He said the forensic work has been challenging as they examine dismembered remains that were in various stages of decomposition when found in the planters.
"I do not want to release this picture and I'm doing so as a last resort", Hank Idsinga of the Toronto Police Service told reporters.
McArthur came under suspicion in September 2017 in connection with the disappearance of Mr Kinsman, but police at first rejected suggestions that a serial killer was prowling Toronto's gay neighbourhood.
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