Apparently adulterated cocaine killed 20 people and left 74 others in hospital in Buenos Aires, health officials said, as authorities searched frantically for the remainder of the deadly batch to get it off the streets before it is consumed.
Experts were still analysing the drug to determine what was in it that caused the deaths.
Judicial officials said one hypothesis being considered was that the cocaine was intentionally adulterated as part of a settling of scores between traffickers.
Police said that the cocaine was sold in the poor neighbourhood “Puerta 8” in San Martin – a suburb to the north of Argentina’s capital – and that a dozen people had been arrested.
“This event is absolutely exceptional. We have no precedent,” San Martin Attorney General Marcelo Lapargo told cable channel Todo Noticias.
“If the situation has escalated and the nature of trafficking has changed to the point where this becomes commonplace, I hope I never see it again.”
Argentine authorities initially reported that eight members of the same group had died after buying the drug on Tuesday. But as time passed, the number of deaths grew.
The province’s health ministry said early on Thursday that 20 people had died and 74 more were in the hospital, with 18 of those requiring mechanical respiration.
“The urgency is to remove the poison from the market, to stop it from being sold,” Mr Lapargo said.
“There must be a lot of people with a bag in their pocket and the number of people hospitalised shows that the most important thing is to stop this extremely high risk.”
Authorities urged anyone who might have bought the deadly drug not to use it.
Sergio Berni, the security minister for Buenos Aires province, called on “those who have bought drugs in the last 24 hours to discard what they bought”.