Accused Canadian serial killer Bruce McArthur has been charged with a seventh murder after the victim's remains were reportedly identified as those hidden inside large planters the landscaper used (Photo: AFP)

A Canadian landscape gardener accused of serial killings targeting Toronto's gay community was charged Wednesday with a seventh murder, as police reopened 15 cold homicide cases dating back decades in search of links.

"We don't know how deep this is going to go," lead investigator Sergeant Hank Idsinga told a news conference when asked if the number of victims was expected to rise further.

"The majority are gay men," he said in reference to the cold cases, which date from 1975 to 1997.

Suspect Bruce McArthur, 66, made a brief appearance via video link from a detention center, as the new charge was announced in a Toronto court.

The charge relates to Abdulbasir Faizi, who was 42 at the time of his disappearance in December 2010.

Faizi's remains were identified among the dismembered body parts found hidden inside some 20 planters belonging to the accused.

The remains of several men who went missing from downtown Toronto's Gay Village have previously been identified in the planters, located on a midtown property used by McArthur to store his landscaping supplies.

According to local reports, Faizi's car was found in early 2011 not far from the property, whose garage has become ground zero for the investigation.

Idsinga said pathologists have matched three more identified victims to their remains, bringing the total number to six, including McArthur's former lover Andrew Kinsman, 49.

The others are Dean Lisowick, 47, and Salim Esen, 44 -- both newly identified -- as well as Skandaraj Navaratnam, 40, and Soroush Mahmudi, 50, and Faizi.

The body of a seventh victim, Majeed Kayhan, 58, has yet to be found and pathologists are still trying to identify another set of remains from the planters.

"These remains are of individuals who have been dismembered," Idsinga said.

"They are in various stages of decomposition and doctors from the Ontario Forensic Pathology Service have been doing some very difficult and time-consuming work in attempting to reconstruct these remains and identify them," he said.

New evidence, according to police, suggests Lisowick was killed in April 2016. The others had been reported missing at various times over the past eight years.

- A possible eighth victim -

McArthur first came under suspicion in September 2017 in connection with Kinsman's disappearance, but police at first rejected suggestions that a serial killer was prowling Toronto's gay neighborhood.

According to local media, police made a quick decision to enter McArthur's apartment and arrest him on January 18 when they saw a young man enter his home. Police found the man tied up on a bed, but unharmed.

Last month, police asked for the public's help in identifying a possible eighth victim from a photograph believed to have been taken after his death.

The man appeared to be in his 40s or early 50s, with dark hair, a beard and bruises on his face.

Police would not comment on the origin of the photo, described as a key piece of evidence.

On Wednesday, police sergeant Idsinga said they have narrowed the number of possible leads to his identity to 22, and offered a sketch of what he might have looked like alive.

"I'd like to get a timeframe and establish that he is in fact deceased" before laying an additional murder charge, he said.

There are 20 investigators working on the case, scouring McArthur's Toronto eastside apartment "inch by inch," Idsinga said.

Authorities have also expanded the number of private and public properties linked to McArthur that they are planning to search from 30 to 75.

In early May after the frozen ground thaws, police will bring in cadaver dogs and start excavating some of them in search of more victims.