South African authorities are seeking answers after 21 under-age teenagers reportedly celebrating the end of school exams died in a mysterious incident at a nightclub.

The bodies of many of the victims, the youngest just 13, were discovered by police lying on tables, slumped over chairs and sprawled on the floor of the club in the early hours of Sunday.

Police spokeswoman Colonel Athlenda Mathe said the investigation into the deaths at the Enyobeni Tavern, in the city of East London in Eastern Cape province, is continuing and no cause of the deaths has been established.

South Africa Nightclub DeathsA teenager is carried out of the nightclub (AP)

Police minister Bheki Cele said forensic samples taken from the victims were being sent to a toxicology laboratory in Cape Town, indicating that officers were investigating whether the victims had ingested a poison or toxin. Mr Cele said the toxicology tests might take “a lot of time.”

Provincial safety official Unathi Binqose told the Daily Maverick newspaper that the victims may have ingested a toxic substance through alcohol they were drinking or through hookah pipes, which were being smoked at the party.

Initial reports speculated that the teenagers may have died in a stampede because of overcrowding, but authorities found no visible injuries on the bodies.

Police said they were called to the nightclub at around 4am on Sunday after receiving a report that there were “lifeless bodies” there.

Officers responding to the call walked in on a grim scene with 17 teenagers found dead on the spot. Two more died at a local clinic, one died on the way to the hospital and one at the hospital. They were aged between 13 and 17, police said.

The teenagers were reportedly celebrating the end of mid-year exams, a local DJ’s birthday and the relaxing of Covid-19 restrictions in South Africa, announced earlier in the week.

South-Africa-Nightclub-Deaths(AP Graphics)

Parents were asked to go to a mortuary to identify their children.

Mr Cele visited the nightclub and the mortuary on Sunday and choked back tears as he spoke to reporters outside.

“The scene I have seen here inside, it doesn’t matter what kind of a heart you have,” he said. “Firstly, the sight of those bodies sleeping there. But when you look at their faces you realise that you’re dealing with kids, kids, kids.

“You’ve heard the story that they are young but when you see them you realise that it’s a disaster. Twenty-one of them. Too many.”

President Cyril Ramaphosa, who is in Germany for the G7 summit, offered condolences to the families in a statement, but also said he was concerned why “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”.

It is illegal for anyone under 18 to consume alcohol in South Africa and residents and community leaders have called for the nightclub to be shut down.

The tragedy will put renewed scrutiny on the many bars and nightclubs operating in poor neighbourhoods in South Africa which are often criticised for not abiding by liquor laws.