Toronto investigators have charged Bruce McArthur with three additional counts of first-degree murder, and say more charges may be pending as they search large planters around the city for human remains. The new charges are in connection with the deaths of Majeed Kayhan, Soroush Mahmudi and Dean Lisowick.

Authorities told reporters on Monday that they have recovered the remains of three unidentified bodies from a property connected to McArthur, a 66-year-old self-employed landscaper.

“These remains have not yet been identified,” Det. Sgt. Hank Idsinga said at a news conference Monday. He said the remains were recovered from large planters at a residence McArthur is known to have used for storage.

“They’ve been hidden in the bottoms of these planters,” Idsinga said.

Idsinga acknowledged that it’s fair to characterize the string of murders as a serial killing.

“It’s a serial killer – alleged serial killer,” he told reporters, adding: “The City of Toronto has never seen anything like this.”

Kayhan, 58, had been among three missing men sought as part of the Toronto Police Service’s Project Houston, which was launched in 2012.

Mahmudi, 50, was reported missing by his family in Scarborough in 2015.

Lisowick was never reported missing, but Idsinga said it’s believed he was killed at the age of 43 or 44, sometime between May of 2016 and July of 2017. “He was an occupant of the shelter system in Toronto,” Idsinga said.

Idsinga said McArthur is known to have worked at 30 different properties within Toronto. Police have contacted the owners of those properties and have searched the majority of them, but are encouraging others who may have employed him to contact investigators.

“We do believe there are more, and I have no idea how many more there are going to be,” Idsinga said. “We’ll lay more charges as we get them.”

Police have not indicated the exact nature of the evidence that led to the charges. However, a source tells CTV News that photographs of the alleged victims were also found at McArthur’s residence.

McArthur was charged on Jan. 18 in connection with the deaths of Andrew Kinsman, 49, and Selim Esen, 44, who went missing last summer from Toronto’s gay village. Their bodies have not been found.

Idsinga said the murders do not all fit a clear pattern, as not all of them are Middle Eastern or members of Toronto’s gay community.

“It certainly encompasses more than the gay community – it encompasses the city of Toronto,” he said.

Police are now looking at disappearances from at least as far back as 2010.

Kayhan was one of three missing men who was never found as part of Project Houston. Skandaraj Navaratnam, 40, and Abdulbasir Faizi, 42, were also sought as part of the investigation, and have not been found.

Court documents brought to light last week indicate that McArthur has an assault conviction dating back to an incident from 2001. The self-employed landscaper was found guilty of one count of assault causing bodily harm and one count of assault with a weapon. He was handed a two-year conditional sentence in 2003 and ordered to receive counselling. He was also barred from visiting Toronto’s Church and Wellesley neighbourhood, and from spending time with male prostitutes.

The first-degree murder charges against McArthur have not been tested in court.