Toronto police say investigators collected more than 1,800 pieces of evidence from the apartment of alleged serial killer Bruce McArthur, as part of what the force is now calling the "largest forensic examination" in its history.

Officers have now finished an inch-by-inch search of the apartment, which started after McArthur's arrest in mid-January. In addition to the items recovered, police said they took some 18,000 photographs inside the Thorncliffe Road apartment McArthur rented near Toronto's Don Valley.

"Our team is tired, but proud," said Det. Sgt. Hank Idsinga, who is leading the investigation.

Police provided no details about what evidence was collected or what was photographed.

Sources told CBC Toronto that a restrained man was found inside McArthur's apartment at the time of his arrest. Officers had been watching McArthur at the time, and were concerned the man was in "imminent danger."

McArthur, a 66-year-old landscaper, has been charged with eight counts of first-degree murder in connection with the disappearances of a number of men, many of whom were connected to Toronto's Gay Village.

McArthur is accused of killing these eight men. Top row, from left to right, Skandaraj Navaratnam, Andrew Kinsman, Selim Esen and Abdulbasir Faizi. Bottom row, from left to right: Kirushna Kumar Kanagaratnam, Dean Lisowick, Soroush Mahmudi and Majeed Kayhan. (Toronto Police Service/CBC)

McArthur is accused of killing the following men: Skandaraj Navaratnam, 40, Andrew Kinsman, 49, Selim Esen, 44, and Abdulbasir Faizi, 44, Kirushna Kumar Kanagaratnam, 37, Dean Lisowick, 47, Soroush Mahmudi, 50, and Majeed Kayhan, 58.

Police say they have found the remains of seven of those men, but not Kayhan's.

Extensive forensic work

Idsinga said the extensive forensic work was performed by 10 officers, with two of them on the scene every day.

"You can imagine when you open the door to that place, you're proceeding inch by inch going into the premises, literally, examining every square inch," Idsinga said. "It's extremely labour intensive when you tackle a scene like that."

Examining McArthur's apartment also required a different approach from going through a scene where a crime is thought to have recently taken place, as the alleged murders in the case date back several years.

"Hypothetically speaking, let's say you have an apartment where you know a murder has taken place, you're going to go in and you're going to be looking for trace evidence such as blood, hair, fibres, DNA, and get focused on a particular area by doing a visual overview very quickly," Idsinga explained.

"You're not looking at a place like this ... we're alleging our oldest murder is over eight years ago in 2010 and we don't know if it occurred there or not. But if Skanda Navaratnam was killed in that residence and there is one hair belonging to Skanda Navaratnam that is still present somewhere, you better find that hair.

"It's definitely a bigger task than a regular murder scene," he added.

Outdoor search ongoing

The remains of some of the men turned up in garden planters at a home where McArthur worked. Cadaver dogs are also searching dozens of other properties.

On Monday, there were no more police investigators in anti-contamination suits, but a security guard kept an eye on the 19th floor apartment where McArthur used to live. The door to the apartment is still caked with dust — possibly from an attempt to find fingerprints.

Idsinga said police completed the search of the apartment on Friday and gave McArthur's family and his roommate time to clear out belongings before turning the unit over to property management.

Police said the investigation is ongoing.

McArthur is scheduled to return to court May 23.