Mass deaths due to an unknown drug are reported among the residents of the Finnish cities of Turku and Helsinki, according to Lenta.ru.
Police in southwestern Finland have reported five drug-related deaths among young people in Turku in April.
Yle newspaper reported ten deaths.
According to Turun Sanomat newspaper, the poisonous substances have killed about 50 people in the capital Helsinki.
The A-Clinic Foundation has warned against selling drugs on the black market that appear to be life-threatening. Researchers have found fentanyl—an opioid analgesic used in anesthesiology—in them.