A young woman was in critical condition at Nikaia General Hospital near Piraeus after being raped in Zefyri, western Athens, it was revealed on Saturday.
According to police, the woman, who is believed to be Roma (either Bulgarian or Romanian), was found unconscious in the street on Wednesday.
A report by a medical examiner said that the woman had drugs in her system before she was sexually assaulted, apparently by several individuals.
What is unclear, sources said, is whether she took the drugs herself or was drugged by her attackers.
Police were examining footage from traffic cameras in the area in a bid to identify the perpetrators.