Hank Idsinga said that the alleged killer had worked on covering up the murders, which meant that additional searches were needed.
DS Idsinga added: 'The city of Toronto has never seen anything like this, it is unprecedented and draining.
Police have conducted interviews with three people who were in sexual relationships with the 66-year-old, all of whom reportedly said they called it quits because they were uncomfortable with some of the sex acts.
"We just hope the remains are just in the planters so they go away and not in the ground", Fraser said.
Officers are also continuing to search McArthur's apartment and will be there "for quite some time", Idsinga said.
Idsinga did not provide any details about a possible relationship between McArthur and any of the three new victims.
He also said that it could take months for the human remains found so far to be identified. They said they were planning to excavate at two locations "where people might be buried", but said they did not know what, if anything, they might find.
"I've actually had some conversations with some citizens from the Church and Wellesley area, and they're feeling more of a sense of relief rather than fear", Idsinga said.
"They cannot be identified because they are skeletal remains and they have been dismembered, We have to wait for DNA tests and we have to get DNA tests from the people that are outstanding and their family members before we can identify those remains", Idsinga said.
None of the information about the circumstances of McArthur's arrest has been officially released by Toronto police.
The Ministry of the Attorney General said McArthur's lawyer is Jeffery Couse. "I can't give you any idea about a number, but I do expect more charges to be laid".
He didn't report the incident to police, but after learning of McArthur's arrest he talked to an investigator. He said he never heard from McArthur again.
"We're shocked that the person that we knew as little as we did would be an alleged serial killer of course we're shocked and we're saddened", Vian Ewart told Global News.
Police officers, who had McArthur under surveillance around 10:25 a.m. on January 18, did not take any chances when they saw a "young man" enter McArthur's 19th-floor Thorncliffe Park apartment.