At least 20 people have died in Argentina after consuming cocaine suspected of containing a poisonous substance.

Cases have been clustered around several towns in Buenos Aires province, officials and local media said on Wednesday February 2.

Another 56 people have been hospitalised, a government source said, adding that more are seeking hospital care in eight of the province’s municipalities due to the toxic cocaine.

The source said the death toll,  currently from the towns of Hurlingham, San Martin, and Tres de Febrero, will likely rise further.

Buenos Aires province, the country’s most populous, is home to many suburbs of the national capital of the same name.

Officials believe some of the victims suffered from opioid intoxication, according to a statement from the province’s health ministry released on Wednesday.

The number of those hospitalised with serious illness is “constantly rising,” it added.

Provincial security forces detained some people suspected of selling the drug after the first deaths occurred on Wednesday.

Some local media outlets reported that the cocaine had been “cut” with a toxic substance, likely by a drug gang looking to reduce costs amid a turf war with rival groups.

“We are waiting for the laboratory results and the results of the investigations into the people who have been detained,” Sergio Berni, the province’s security minister, told local television.

The local government of Tres de Febrero said in a statement it was aware of people falling seriously ill due to “allegedly adulterated cocaine” and was working with emergency services and hospitals to prevent more deaths.