Authorities in South Africa on Monday said that the 21 teenagers found dead at a nightclub in the coastal town of East London were probably killed by something they ate, drank or smoked. They further ruled out the possibility of a stampede. 

The cause of death, however, still remains unexplained. 

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The police said they were still investigating the case.  The teenagers were reportedly attending a party to celebrate the end of winter school exams. Local newspaper Daily Dispatch reported that bodies were strewn across tables and chairs without any visible signs of injuries.

The spokesperson for the Eastern Cape’s provincial community safety department, Unathi Binqose, told Reuters that poisoning could have caused the death. 

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“It is either something they ingested which will point to poisoning, whether its food or drinks, or it is something they inhaled.  We are ruling out a stampede completely,” Binqose said. 

Meanwhile, Eastern Cape Premier’s office told CNN that four people remain in critical condition. Five bodies are still unidentified.

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Police minister Bheki Cele said the victims’ ages ranged from 13 to 17, raising questions about why the underaged teenagers were being served alcohol.

President Cyril Ramaphosa expressed condolences to the families of those who died.

“The President is, however, concerned about the reported circumstances under which such young people were gathered at a venue which, on the face of it, should be off limits to persons under the age of 18,” Ramaphosa said in a statement.

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The owner of the club, Siyakhangela Ndevu, told local media he was called to the scene early Sunday morning.

“I am still uncertain about what really happened, but when I was called in the morning I was told the place was too full and that some people were trying to force their way into the tavern,” he said. “However, we will hear what the police say about the cause of death.”