At least 21 teenagers died over the weekend after a night out at a township tavern in South Africa, officials said Sunday.

Although the cause of the deaths is still unclear, local officials and politicians said they feared this might have been a case of under-age drinking that went tragically wrong.

The provincial government of Eastern Cape said eight girls and 13 boys had died at the tavern, in a residential area called Scenery Park. Seventeen were found dead at the scene, while the rest died in hospital.

Empty bottles of alcohol, wigs and even a pastel purple "Happy Birthday" sash were found strewn on the dusty street outside the double-storey Enyobeni Tavern, said Unathi Binqose, a safety government official who arrived at the scene at dawn. 

Many of the victims are thought to have been students celebrating the end of their high-school exams on Saturday night, officials said.

There were no visible wounds on the bodies, but autopsies would determine if the deaths could be linked to poisoning, they added.

Among the senior government officials who rushed to the southern city was Police Minister Bheki Cele. 

He broke down in tears after emerging from a morgue where the bodies were being stored.

"It's a terrible scene," he told reporters.

"They are pretty young. When you are told they are 13 years, 14 years and you go there and you see them. It breaks (you)."

Under-age drinking suspected 

Drinking is permitted for over-18s.

But in township taverns which are often situated cheek by jowl with family homes, safety regulations and drinking-age laws are not always enforced.

"We have a child that was there, who passed away on the scene," said the parents of a 17-year-old girl.

"This child, we were not thinking was going to die this way. This was a humble child, respectful," said grieving mother Ntombizonke Mgangala, standing next to her husband outside the morgue.

President Cyril Ramaphosa, who is attending the G7 summit in Germany, sent his condolences.

He voiced concern "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".

The authorities are now considering whether to revise liquor licensing regulations.

South Africa is among the countries in Africa where most alcohol is consumed.

Provincial prime minister Oscar Mabuyane condemned the "unlimited consumption of liquor".

"You can't just trade in the middle of society like this and think that young people are not going to experiment," he said outside the tavern.

'No obvious signs of injury'

Commenting on the tragedy the tavern's owner, Siyakhangela Ndevu, said: "It's not something that as a businessman, I expected to have happened there, but things like this happen unexpectedly."

There had been a rush to enter the bar by revellers despite warnings it was full, he told reporters.

He was called to the scene after 1:00 am (2300 GMT) as there were "too many people. Others want to go out and others ...want to forcefully enter".

But safety official Binquose ruled out a stampede as the cause of death.

"There are no visible open wounds," he told AFP.

"Forensic (investigators) will take samples and test to see if there was any poisoning of any sort," he said.

The regional liquor licensing agency said it was considering revoking the tavern's licence and laying criminal charges against the owner for "blatant" contravention of the law that prohibits the sale of alcohol to under 18's.

Local newspaper DispatchLive reported on its website bodies "lying strewn across tables, chairs and on the floor, with no obvious signs of injury".

Some of the dead were students celebrating "pens down" parties held after the end of the mid-year exams.

A crowd of people gathered outside the club in the city, which is located on the Indian Ocean coast, nearly 1,000 kilometres (620 miles) south of Johannesburg.