At least 21 teenagers died over the weekend after a night out at a township tavern in South Africa, officials said on 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 the 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 others 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, according to 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)." (AFP)