With alleged serial killer Bruce McArthur now accused of killing seven men, Toronto police say there's still a possibility of more victims as they prepare to search 75 properties and look into cold cases going back 40 years.

"We really don't know how deep this is going to go. We just don't know yet," said lead investigator Det-Sgt. Hank Idsinga on Wednesday.

In a Toronto courtroom earlier in the day, McArthur, 66, was charged with first-degree murder in the death of Abdulbasir Faizi, who went missing in 2010.

Faizi was 42 when he disappeared. He frequented Toronto's Gay Village, but kept his nightlife hidden from his family, according to his nephew, Bobac Faizi.

Abdulbasir Faizi went missing in 2010. His family says he kept his nightlife hidden. (Toronto Police Service)

Police said they believe McArthur and Faizi knew each other.

At a news conference Wednesday to provide new information about the investigation, police also said they have identified three more of the at least seven sets of remains found at a midtown Toronto property where McArthur worked as a landscaper and stored tools.

Idsinga told reporters the dismembered remains of Selim Esen, Dean Lisowick and Faizi have been identified.

Bruce McArthur is now accused of killing these seven men. Top row, from left to right, Skandaraj Navaratnam, 40, Andrew Kinsman, 49, Selim Esen, 44, and Abdulbasir Faizi, 42. Bottom row, from left to right: Dean Lisowick, 47, Soroush Mahmudi, 50, and Majeed Kayhan, 58. (CBC/Toronto Police Service)

Police had previously identified the remains of Andrew Kinsman, Soroush Mahmudi and Skandaraj Navaratnam.

McArthur was arrested in January, accused of preying on men in the LGBTQ community who hung out in the downtown Gay Village.

The other charges relate to the deaths of Mahmudi, 50, Kinsman, 49, Navaratnam, 40, Esen, 44, Lisowick, 47, and Majeed Kayhan, 58.

Police have not ruled out the possibility that the seventh set of remains, which Idsinga described as being in "various stages of decomposition," belong to Kayhan.

The men went missing between 2010 and 2017.

Search for unidentified man continues

On Wednesday, police updated the public on several aspects of the investigation, including their ongoing push to identify a deceased man who they released a graphic image of last month.

Idsinga said Wednesday that investigators received hundreds of tips about the identity of the man in the photo, and have since whittled down the list to 22 possible identities.

Police also released an enhanced photo of the man to aid in his identification, with Idsinga thanking activist Nicki Ward for her help in touching up the picture.

Idsinga said investigators needed to identify the man so they could pursue "possibles" with hopes that DNA or dental records would match up with found remains.

He also said it's possible the man is not from Toronto.

A police source previously told CBC Toronto the image of the man was among a cache of images of alleged victims found on McArthur's computer, though on Wednesday Idsinga refused to confirm that information.

Police are also filling in the blanks as to the exact fate of Dean Lisowick, who was never reported missing to police.

On Wednesday, Idsinga said that Lisowick was killed in April 2016.

Search for clues continues

Investigators haven't found any new remains, but have new information on what they've uncovered. (Chris Young/Canadian Press)

The city-spanning search for evidence will likely ramp up in May as police prepare to search 75 pieces of both public and private property with canine units, including a number of houses where McArthur did landscaping work. Excavations of the properties will be determined by what the dogs pick up, Idsinga said.

Police are also now finished searching about 20 planters seized from various locations around the city, with no additional remains discovered inside.

Investigators are still going through McArthur's Thorncliff Park apartment "inch by inch," Idsinga said.

The Fifth Estate | It happened before: Unsolved murders in Toronto's Gay Village

Police are also still reviewing cold case files dating back to the 1970s involving gay men who were slain in Toronto's downtown core after leaving bars popular in the LGBTQ community. Most of the men were stabbed to death and found naked in their beds.

McArthur would have been in his twenties at the time.

Idsinga told reporters Wednesday the police are looking into 15 cases from between 1975 and 1997 and are working on a detailed timeline of McArthur's whereabouts over the years.

He had previously told the CBC's The Fifth Estate that he "wouldn't be surprised" if McArthur is linked to more killings.

Statistically, most serial killers start committing crimes in their 20s or 30s.

Some of the men McArthur is accused of killing kept their sexuality hidden from their families, were new to Toronto or had few ties to the community.

John Lancaster can be reached at john.lancaster@cbc.ca or at 416-205-7538