The procedures involve injecting a substance into the body that is advertised as PMMA or polymethylmetacrylate to enhance the appearance of their buttocks, police said in a public safety alert released on Monday.
"This type of procedure performed outside a medical facility is very dangerous and could result in long-lasting complications and, in some cases, even death," police said in the statement.
Appointments and arrangements are usually made via email or referral, police said. The injector will go to the client's home or a hotel room to perform the procedure.
The services are typically paid for in cash, usually costing "thousands of dollars," police said.
"Some of these women have developed serious medical complications requiring hospitalization," it said.
Dr. Sammy Sliwin, a Toronto plastic surgeon, told CBC News he is concerned by recent cases of women coming to see him after getting injections of what they are told is PMMA.
Quality of illegal injections questionable, doctor says
PMMA is a fibreglass-based augmenter, normally used in small amounts in lips, reported the CBC's Peter Akman.
But the women who have come to Sliwin for help are unsure what exactly was used in their enhancements.
"We asked her what it was, she had no idea," he said. "She said someone came up from Miami to inject her. I asked, 'was it a doctor?' She said, 'I have no idea.'"
Toronto police say a black market for these injections has sprung up in the city.
"They are prevalent for women in the entertainment industry, the exotic dancing industry," said Toronto police Detective Louise Farrugia.
Based on price alone, most plastic surgeons doubt that it is actual medical grade PMMA being injected, Akman reported.
A silicon butt enhancement would cost roughly $8,500, and an injection of a person's own fat would cost $6,500. But for medical grade PMMA, the cost could reach about $75,000, Akman reported.
"I am just not sure what the quality is," said Sliwin.
Anyone with information about these illicit procedures is asked to contact police or Crime Stoppers.