Investigators are searching through garbage for evidence at a waste transfer station and are also searching two apartments, which they describe as potential crime scenes.
Det. John Margetson says they are still looking for about two-thirds of the woman's remains but aren't sure they will be found.
"There's indications of forensic evidence at both scenes," he said, but added the death can't be ruled a homicide at this time.
A post-mortem has been conducted but the cause of death has not been determined.
Police say they are treating the death as suspicious and will not be releasing the woman's name until a forensic examination confirms her identity and her family is notified.
The man charged in the case, Adonay Zekarias, 41, was arrested at his home Sunday and was remanded in custody on Tuesday pending a court appearance on May 30.
Margetson says the suspect and the person believed to be the victim were known to each other and that they both came from the African country of Eritrea but had lived in Canada for a while.
Investigators are not sure exactly when the woman died but Margetson said it was sometime in the last two weeks.
"At this time all we have is the remains found in the duffel bag and obviously we are searching for the rest of the remains," Margetson said, adding it's believed the bag was "walked" into the trail area and left there.
But he admitted he wasn't confident police would be able to find other remains, due to the amount of time that had passed and the removal of garbage from the apartment buildings.
"That area that the remains were found, our dog handler said there were coyotes in the area," he said, adding the other remains "could be anywhere in the city or outside the city."
Eight dumpsters have already been searched in the city's west end, he said, but due to the time frame involved, garbage may already have gone to transfer stations or could even have been taken to a dump in London, Ont., by now.
Margetson said it's not yet known whether the search will be expanded to the London area.