(CNN) As Toronto police combed through more than a dozen planters and worked to thaw frozen ground in their search for human remains, investigators continued Friday to piece together what they believe is the puzzle of a serial killer and his victims.

The killer had some sort of relationship with each of his male victims, some of which were sexual, Toronto Police spokeswoman Meaghan Gray said Friday.

Bruce McArthur, a 66-year-old landscaper, has been charged with five counts of murder and accused of hiding his victims' remains in potted plants in Toronto.

"We do believe there are more (victims)," homicide detective Sgt. Hank Idsinga said last week. "And I have no idea how many more there are going to be."

So far, McArthur is accused of killing Andrew Kinsman, 49; Selim Esen, 44; Majeed Kayhan, 58; Dean Lisowick, 47; and Soroush Mahmudi, 50. But police have said more victims could be discovered soon.

Investigators found the remains of three victims in potted plants last week, and police said they had found at least three more remains on Friday. Of those six sets of remains, one has been identified as belonging to Kinsman. The five other remains are still unidentified.

Police said even though remains recovered so far have not been linked to the four men named as victims in addition to Kinsman, investigators have "sufficient evidence" to believe they were killed.

All of the remains found so far were located at one property where McArthur stored his landscaping equipment. The expanding investigation is now focusing on that property and one other location closely connected to McArthur.

Both locations will be excavated by investigators for evidence, but the excavation of one property has been partly held up by the frozen winter ground in Toronto, where it was 23 degrees Fahrenheit (minus-4 degrees Celsius) Friday afternoon. Toronto police said they have been heating the ground at that property for over a week to thaw it and allow for a fuller excavation.

In addition, police have seized a total of 15 planters from several properties that investigators say could contain more evidence or remains. McArthur is connected to up to 30 properties, and officials have asked more of his landscaping clients to come forward.

The grisly details and the number of victims led police to refer to McArthur as an alleged serial killer.

"The city of Toronto has never seen anything like this. The resources that are being thrown at it, everything that we have," Idsinga said. "I'd call it an unprecedented type of investigation."

CNN called McArthur's attorney on Thursday but did not get a response.

Impact on LGBTQ community

The five victims have been identified as, from top left, Majeed Kayhan, 58; Dean Lisowick, 47; Soroush Mahmudi, 50; Selim Esen, 44 and Andrew Kinsman, 49, according to Toronto Police Service.

Police said both Esen and Kinsman were active on social media dating applications. Because the killings targeted members of Toronto's LGBTQ community, more than a dozen affiliated groups organized a community vigil on February 13 to grieve.

"This is of course a terrible tragedy, but not the first time the LGBTQ (community) has lost lives and members of the community have been missing," said Soofia Mahmood of the 519 Center, the center of the LGBTQ community in Toronto.

"The community has been victim to systemic abuse over the years, particularly people of color in our community. There is need to expect and demand accountability, from police and other groups who stereotype members of the community," Mahood said. "But now, there is a need for solidarity in the community. We need to come together to celebrate the community and heal together."

McArthur was first arrested on January 18 and charged with two counts of murder in connection with the deaths of Kinsman and Esen, two men who went missing last year. On January 29, McArthur was charged with three more counts of murder for the killings of three other missing men dating back to 2012.

Kayhan was reported missing in October 2012. Lisowick was never reported missing, but authorities believe he was murdered sometime between May 2016 and July 2017. Mahmudi was reported missing in August 2015.

Esen had no fixed address, and often had a small plastic suitcase on wheels, police said. He was reported missing in April last year.

And Kinsman was last seen in June 2017.

"I got a text from one of his housemates on June 28, saying no one had heard from him for a couple days," Ted Healy, a friend of Kinsman's, told CNN. Healy said he subsequently went into Kinsman's apartment to find a hungry cat but nothing else amiss. "The cat was out of food and water and was glad to see us," Healy said. "The apartment was untouched."