Adulterated cocaine has killed at least 20 people and left 74 in hospitals around the Buenos Aires region of Argentina, the authorities say, BBC reported.

Investigators believe the illegal drug was either laced with some kind of poison or "cut" with another substance.

The regional security minister called on any users who had bought cocaine in the past 24 hours to throw it away.

Reports suggest the drugs were bought in the same shanty town, and nine arrests have been made.

Investigators are awaiting the results of post-mortem examinations to compare drugs seized in raids with those consumed by the victims.