Hundreds of pages of police documents, released by a judge on Monday, show that Toronto police were actively investigating, and perhaps tracking, accused serial killer Bruce McArthur months prior to his arrest in January.

CTV News Toronto is one of several media organizations that acquired the files. The redacted documents show that tracking orders for phones and vehicles associated with the investigation were issued as early as September 2017.

Former police investigator Mark Mendelson said these warrants allow police to physically track a suspect without risking the prospect of being discovered.

“Once the suspect realizes they are being followed, they change their habits completely,” he said. “These types of tracking warrants allow the police to allow GPS devices on vehicles, whether it’s a car or a bicycle or a motorcycle, in order to track those movements lawfully?.”

Police were also granted production orders for Google, Rogers, Bell, Telus, Royal Bank, and Manulife Bank in August and September 2017. Production orders obtained after judicial authorization compel organizations to release information to the police.

In October, further orders were granted for production from Transunion Bank, the Bank of Nova Scotia, TD Bank, and Pink Triangle Press – a publisher that specializes in LGBT material.

On Dec. 4, 2017 investigators obtained a general warrant for McArthur’s apartment. According to Mendelson, this kind of warrant would include fingerprints, hair, bodily fluids, computer data, pictures and video, among other things.

It is not clear if investigators entered the apartment before Jan. 18, 2017, when McArthur was taken into custody.

McArthur has been charged with the first-degree murder of eight men who police believe were killed between 2010 and 2017.

He was first charged in connection with the deaths of Andrew Kinsman and Selim Esen. Both men were reported missing from Toronto’s gay village in 2017.

McArthur was also charged in connection with the deaths of Majeed Kayhan, Soroush Mahmudi and Dean Lisowick a few weeks later. In February, police laid charges in the death of Skandaraj Navaratnam and in April two more charges were added in connection with the deaths of Abdulbasir Faizi and Kirushna Kumar Kanagaratnam.

Many of the murdered men had a connection to Toronto’s LGBTQ community and were previously reported missing.

In a public statement on Dec. 8, 2017, Police Chief Mark Saunders downplayed the idea that a serial killer could be targeting Toronto’s gay community.

The remains of at least seven of these men were discovered in planters on a Leaside property where McArthur worked as a landscaper.

Investigators wrapped up their investigation of McArthur’s 19th-floor Thorncliffe Park apartment in early May and say they have collected more than 1,800 exhibits of evidence and taken 18,000 photos.

Last week, police completed a canine search of over 100 properties connected to the case.

The documents obtained by CTV News Toronto were unsealed by a judge after a media group, including CTV, appealed for access. Large portions of the documents remain sealed, including what investigators were searching for with each warrant and the summary of evidence that led to the authorization of the warrants.

McArthur is scheduled to appear in court again on June 22. None of the allegations have been proven in court.

With files from CTV’s Scott Lightfoot