Forensic personnel load bodies of victims after the deaths of patrons found inside the Enyobeni Tavern, in Scenery Park, outside East London in the Eastern Cape province, South Africa. [Reuters]

Chemical poisoning caused the death of at least 21 teenagers at a nightclub in East London, South Africa on Sunday, authorities have said.

According to South African news outlet eNCA, authorities are yet to identify the specific chemical inhaled.

"It is some sort of chemical poisoning that took the lives of these 21 teenagers...They found that in each of these teenagers, there was consistent poisoning," the outlet reported.

The poison the teenagers ingested could have either been inhaled or injected.

The toxicology laboratory in Cape Town is trying to establish the exact toxin that took the teenagers' lives.

On the morning of Sunday, June 26, South African police found 17 bodies in a nightclub while several others were injured.

The death toll has since risen to 21.

At the time, Eastern Cape Police Commissioner Nomthetheleli Lilian Mene suspected there could have been a stampede that led to the incident.