The parents of 21 young people who died at a night club in June have been told they suffocated.

However, it is not clear in the newly released the report what caused the teenagers’ deaths.

“The report has come out but I’m not happy about it,” said Xolile Malangeni, whose 17-year-old daughter, Esinako, was among the victims.

Xolile and others complained that the results were communicated by the authorities to them verbally.

A health department spokesperson for the Eastern Cape province declined to comment on the results of the investigation and told reporters the probe would not be published.

Twenty-one young people – the youngest aged 13 – died while partying at the Enyobeni Tavern in Scenery Park, a township outside the coastal city of East London, Eastern Cape province.

More than 1000 mourners attended the funeral for 19 of the 21 night club victims. Photo: Getty.

Multiple causes for the death of the teens had been flagged in past weeks, including poisoning from what they may have eaten or drunk.

Local news TV eNCA reported on Thursday that asphyxiation had been caused by overcrowding.

In June a source close to the investigation told Reuters the young people may have died by poisoning from a gas leak .

More than 1000 mourners attended the funeral for the victims two weeks after the tragedy and South African President Cyril Ramaphosa delivered a eulogy.

In South Africa the legal drinking age is 18, the owner of the bar has been arrested and charged with supplying minors with alcohol.

-with AAP