Authorities are working to remove a tainted batch of cocaine from the streets of Argentina after at least 20 people were found dead after taking it.

Sergio Berni, security minister for the Buenos Aires Province, said Thursday that a synthetic opioid appears to have been added to intensify the effects of the cocaine, according to the Associated Press. In addition to the dead, health officials said at least 84 people have been hospitalized, many of whom are younger Argentines from poorer neighborhoods around the nation’s capital, Buenos Aires.