Police and the KwaZulu-Natal community safety department are investigating a video of an alleged gang-rape of a high school girl after a matric dance, the department said on Wednesday.

"We are analysing the video and are working together with the SAPS [SA Police Service] to try and identify witnesses," said spokesman Sipho Khumalo.

"We have not yet identified anyone and have to be careful to make sure the name of the school is not known, as this might lead to the victim being identified."

The video was circulated on social media.

Khumalo said the incident happened a week ago. He did not have further details on where in Pietermaritzburg it happened.

Police spokesman Colonel Jay Naicker said the case was being investigated by the SAPS child protection and sexual offences unit in Pietermaritzburg.

"The victim has not yet been identified as well as the culprits. Investigations are continuing, at this stage it is unknown where the alleged incident took place," said Naicker.