The case against seven people, including two minors, accused of gang-raping a mentally ill Soweto teenager was postponed on Thursday in the Roodepoort Magistrate's Court.

National Prosecuting Authority (NPA) spokesman Mthunzi Mhaga said the case was postponed to April 25 for further investigation.

"We need to get a psychiatric report into the mental status of the girl, because for now we don't know for sure whether she is mentally unstable or not," Mhaga told reporters outside court.

"We also need to determine the condition of release in respect of the minors, because there are minors and there are adults involved -- so we have postponed the case to conduct further investigations, because the investigations are at an infant stage."

Mhaga said there were preliminary charges based on the NPA prosecutors' viewing of the video.

"They will be facing several counts of rape, sexual assault, engaging sexual services of a minor for a reward, using a minor to create child pornography, committing a sexual act in the presence of a minor and committing a sexual act in the presence of an adult," he said.

"They will also be facing charges that relate to the contravention of the films and publication act which is creating, possession [of] and distributing child porn."

Court proceedings were slightly delayed in the morning as the police docket arrived after 9am and officials were trying to allocate a courtroom to the case.

The seven were arrested in Dobsonville, Soweto on Tuesday, after they were matched to the descriptions of the rapists seen in a video recording of the attack.

The video of the 17-year-old girl being raped went "viral" on the internet on Wednesday, and was one of the main topics trending on social networking site Twitter.

A group of about 30 women from the African National Congress's Women's League arrived at the court in a bus dressed in ANC colours. They were armed with posters reading: "cut their penis -- no bail", "let them rot in jail" and "done with rapists", and sang struggle songs.

Mhaga briefed the media outside court on what had happened, as the media was barred from court because there are minors involved.