Heroin components have been detected in the bodies of three foreign nationals and a Japanese who died in March and April in Tokyo, police officials said Saturday.

Seven other people, including Americans and Japanese, were hospitalized from March to May for symptoms believed to stem from illegal drugs, the Metropolitan Police Department said.

Heroin traces were found in a 21-year-old female Brazilian dancer who died at a hospital after collapsing in the Roppongi area in March, and the three others — a 46-year-old Canadian man, a 33-year-old American man and a 30-year-old Japanese woman — died in April, they said.

Cocaine traces were also detected in the body of the Canadian man, they said.

Police have arrested several of the people who were hospitalized on suspicion of drug violations and are trying to track down trafficking routes.