The five men who abducted and raped a 30-year-old BPO employee near her home in south Delhi two days ago were seen in the area 20 minutes before the incident took place.
The police have traced another eyewitness in the case - a local resident who saw five men and a white pick-up van parked in the service lane near the crime spot that night.
This eyewitness surfaced after the police questioned all the men living in the area including people working at an automobile shop.
Police said they were not getting much help from the people who may have seen the accused and were conducting door-to-door survey to seek any clue to crack the case.
The friend of the BPO employee, meanwhile, helped the police prepare the sketch of one of the accused.
"After going through a hellish experience, it's she who will bring the guilty to justice - all for a friend whom she helplessly saw being kidnapped in front of her eyes. She is actively participating in the investigations," said a senior police officer.
Police said because of the trauma, the victim's memory is "too fragmented" for her to give an account of the physical appearance of the men. The accused had made an attempt to abduct the friend but she managed to escape.
On Friday, the police detained four men from Mongolpuri area on the basis of suspicion but they were let off after questioning.
The Crime Branch, which is also investigating the case, has launched a massive hunt for the Tata Ace pick up van that was used to abduct the victim. Police said they were also taking technical assistance and were checking the mobile phones active in the area at that time to get any clues.
"It is with the friend's help and other eyewitnesses that we have managed to prepare a sketch of one of the men. They do not have an account of the other four men in the vehicle," said HGS Dhaliwal, deputy commissioner of police (south).
Almost all the wings of the Delhi Police have been pressed into action for this case.
Police said what proved a hurdle in tracking the vehicle the night of the crime was not enough description of the vehicle.