Thousands of young Nigerians are addicted to codeine cough syrup - a medicine that's become a street drug. The government estimates that up to 3 million bottles of the addictive syrup are drunk every day in just two northern states. Taken in excess, codeine can cause psychosis and organ failure.But who makes this syrup? And who sells it to Nigeria's children?In this exclusive investigation, BBC Africa Eye and BBC Pidgin went undercover to find out.Less than 24 hours after this film was screened, the Nigerian government banned the import and manufacture of codeine-based syrup.