Prosecutors in Burkina Faso launched an investigation Monday into how 11 people died in custody overnight in cells at the premises of the anti-drugs unit in the capital Ouagadougou.
Police informed the prosecutor's office on Monday that 11 people held for drugs offences had died overnight, prosecutor Maiza Sereme wrote in a statement.
"An investigation has been opened," and coroners had been called in to carry out autopsies on the victims, she added.
Poverty stricken Burkina Faso is one of the main transit points for drugs arriving from the ports of West Africa, from where it moves north towards the Malian and Libyan desert.
In June, the authorities burned 35,300 tonnes of narcotics: a quarter of the previous year's drugs seizures, according to the Burkina's National Committee for the Fight against Drugs (CNLD).