Cape Town - South African authorities say the owner of a bar where at least 17 teenagers were found dead and four others died while receiving medical care is expected to face charges. Police investigating the mysterious deaths in Eastern Cape province say they have not ruled out the possibility the teenagers were poisoned.

South African police say they are investigating and awaiting autopsy results after the teenagers' bodies were found at a bar early Sunday morning with no visible cause of death.

Brigadier Thembinkosi Kinana is a police spokesman.

"Whilst we understand the urgency of this matter and the anxiety of the public, in particular the affected families who want answers. We urge that we allow sufficient time for our detectives to finalize those investigations. I must also add that we have not made any arrests at this stage," he said.

South African police say the owner is expected to face charges and have not ruled out the possibility that the teenagers were poisoned.

Spokesman Kinana said half-a-dozen of the bodies were not immediately claimed.

"We are making an appeal to parents or relatives who may have not seen their children since the past weekend to please make time to make inquiries. We are also calling upon parents whose children who may have survived the tavern incident but are still feeling sick to please visit hospitals and clinics for medical check-ups," he said.

Police were called to East London's Enyobeni Tavern in Eastern Cape province, where local media reported the bodies were found slumped on the floor and tables.

The tavern's owner, Siyakhangela Ndevu, told AFP news agency that patrons had tried to force their way into the bar despite it already being packed.

But safety authorities were quick to rule out a stampede because of the lack of injuries on the bodies, some as young as 13 years old.

Eighteen is the legal drinking age in South Africa.

Lucky Ntimane is Convenor of South Africa's National Liquor Traders Council.

"The owner had workers working there, he had bouncers, they could've seen, easily seen that there were minors in that establishment. But this was allowed to happen, the owner put the profits before the people. He should never ever trade in alcohol ever in his life. The license should be revoked with immediate effect," he said.

South Africa's President Cyril Ramaphosa expressed condolences for the families through his spokesman Vincent Magwenya.

"While the president awaits more information on the incident, his thoughts are with the families who have lost children. The president is however also 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 people under the age of 18. The president expects the law to take its course following investigations into the tragedy," he said.

He added that the deaths were even more tragic as they happened during South Africa's youth month.

Youth month developed from the June 16 National Youth Day when South Africa reflects on the massacre of students during the 1976 Soweto Uprising against apartheid.

Some of the dead were also students celebrating the end of mid-year exams.