McArthur was first arrested and charged with two counts of first-degree murder on January 18 in connection to the disappearances of Andrew Kinsman and Selim Esen.
Police have said they expect to find more remains in the planters they've retrieved from around the city.
More remains could be found at the Mallory Crescent property when investigators begin to dig with the assistance of a forensic anthropologist, Gray said.
Police said they believe more charges will be laid as they prepare to use ground penetrating radar and canine units as well as large heaters to thaw the frozen ground in the search for more victims.
Authorities have checked at least 30 other places where the landscaper was known to have worked, including some of Toronto's wealthiest neighborhoods.
Police said that some of the remains found on Thursday belong to Kinsman, and are still trying to determine if any of it belongs to McArthur's three other suspected victims.
McArthur, 66, is believed to have preyed on members of Toronto's gay community, and allegedly met some of his victims on dating apps. "We're going through computers".
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"We did go to his apartment that he shared with his ex-partner for dinner once about 12 years ago".
On Thursday (8 February) police told reports that they have recovered the remains of six people and have the DNA profiles of two people, one of which was Kinsman's, but did not say who the other profile belonged to. "We've prepared warrants on different providers, so that's a very big part of this investigation".
On Thursday, McArthur's son, Todd, declined comment to CP24 after appearing in an Oshawa court for an unrelated bail hearing for criminal harassment and indecent telecommunications charges.
The other three known victims are 58-year-old Majeed Kayhan, who went missing in 2012, Soroush Marmudi, 50, who went missing in 2015 and Dean Lisowick, who went missing between May 2016 and July 2017.
Kayhan was reported missing in October 2012.
None of the allegations against McArthur have been tested in court. Both men went missing from Toronto's gay village in 2017. Police are also working with global agencies as McArthur travelled for work.
He also said police were taking a detailed look at McArthur's extensive digital presence.