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The four-month investigation uncovered hundreds of trafficking rings, some of them as small as three or four people, said Chief Superintendent Chiara Giacomantonio.

"There were no surprises. Unfortunately it's all well-known," Giacomantonio said. "It's Albanians exploiting Romanian women, Chinese exploiting Chinese, Africa on Africa."

Most of the people running the operations and their victims came from countries in Eastern Europe, including Moldavia, Albania and Romania, as well as countries in Asia and Africa, Giacomantonio said. Some prostitutes were brought in from Iraq, she added.