Delhi police today claimed to have made a major breakthrough in the gang-rape case of a 30-year-old call centre employee here last week with the arrest of two youths.

Investigators apprehended Shamshad and Usman, who are in their early twenties, from Haryana's Mewat last night while one of their accomplices surrendered in a Ballabgarh court in connection with a cow slaughtering case two days ago.

The incident took place in the wee hours of November 26 when the Mizo woman was walking towards her home in Moti village near Dhaula Kuan in south Delhi along with one of her colleagues when the men in a vehicle abducted her and took turns to rape her. She was later dumped in Mongolpuri.

"We have arrested two persons. We have learnt that another person has surrendered in a Haryana court. We are looking for the other two accused," H G S Dhaliwal, deputy commissioner of police (South) said.

Sources said Shamshad and Usman have a criminal background and were allegedly involved in at least three cases of rape earlier. "These people have criminal background. They were involved in rape cases earlier," they said.

"They matched the sketches also," the sources said.

Investigators have impounded the truck which was allegedly used in the crime.

Asked how investigators zeroed in on the two suspects, a senior police official said they have ascertained the movement of the accused in the locality on the fateful day through technical surveillance.

"We had established their movement in the area on that day through technical surveillance. Once the vehicle was identified, we went to the owner and apprehended the accused," the official said.

More than 500 people have been questioned in the case besides scanning of hundreds of vehicles. Around 400 pick-up vans were scanned in Mongolpuri market itself.

Investigators had been groping in the dark for the past few days despite 15 special teams being formed to nab the culprits. Three sketches were released by police besides questioning several suspects, surfing through CCTV footage and recording statements of three witnesses.

They had also gone through mobile phone records of a number of "possible" suspects residing in Mongolpuri area as they believe that the culprits were "very familiar" with the locality and they could be staying there.