Four pharmaceutical companies have been raided after a report into the role of cough syrup containing codeine in an addiction epidemic.
The firms are in Lagos, Ilorin and Kano, the National Agency for Food and Drug Administration and Control said.
The federal government has this week announced a ban on the production and import of the syrup.
Reports indicate that the syrup being sold on the black market for young Nigerians to get high.
The probe recorded a number of pharmaceutical employees selling the drug illegally.
Prices of the syrup on the black market have shot up since the ban.
Officials estimate that about three million bottles of codeine syrup are being drunk a day in just two states, Kano and Jigawa.
Excessive consumption of codeine can cause organ failure and schizophrenia.