New Delhi, Dec 18 (IANS): CCTV footage from a toll plaza collected by investigators Monday showed that a bus in which a Delhi woman was gang-raped here had gone past the plaza in Gurgaon the night before, police said.

The bus crossed the toll plaza around 10 p.m., a police officer said.

While four people were detained, sketches of two of the accused were prepared with the help of the victim's boyfriend. One of them was identified as Sonu, the officer said.

Deputy Commissioner of Police (South) Chhaya Sharma said the toll plaza CCTV footage confirmed that the vehicle used in the crime was a white luxury or chartered bus and not a regular bus plying on public transport bus routes.

The bus staff were picking up passengers from Munirka to west Delhi and charging Rs.10 per passenger, she said. 

The raped woman, 23, a para-medical degree holder, along with her 28-year-old boyfriend boarded the bus at Munirka around 9.15 p.m. Sunday to go to Dwarka, police said. She was gang-raped in the moving vehicle by five to seven bus crew, police said.

She and her boyfriend were later thrown out of the bus under Mahipalpur flyover in south Delhi's Vasant Vihar area, police said. The rape victim was Monday battling for life at hospital while her friend was discharged after initial treatment, police said.