A girl and a woman were arrested in Soweto on Saturday for allegedly raping a 17-year-old mentally ill boy, Gauteng police said.

The alleged perpetrators had been on the run since last Sunday, Warrant Officer Kay Makhubela said.

One of them, also aged 17, was taken to a place of safety.

Makhubela said police suspect the boy was drugged.

"After the rape the boy told his granny what happened and she immediately came to police," he said.

Makhubela said this rape was similar to three other unresolved cases which involved women drugging and raping men.