A 25-year-old man and a 24-year-old woman were arrested from their apartment in which dangerous substances such as fentanyl were found.
Jukka Larkio, the lead investigating officer, said the interrogation of the two was underway.
Some of stolen drugs were yet to be found.
The drugs which were used for research were stolen from the University of Helsinki Viikki campus premises last week. The drugs are considered to be exceptionally dangerous.
In addition to fentanyl, other drugs such as heroin, morphine, cocaine, amphetamines and lysergic acid diethylamide (LSD) were stolen.
The police also suspect that the death of a man which occurred a week ago might have resulted from the use of the drugs. The suspect and the victim were known to each other.
