Though five persons have been arrested for the alleged rape of a nun in riot-hit Kandhamal, the Orissa police found it tough in tracing her and finally asked its all-women team to return from Delhi [Images] on Wednesday after a futile search there.

Official sources said, "We have been unable to trace the alleged rape victim so far. The police had formed three teams to trace the nun," Home Secretary T K Mishra told PTI.

He said efforts were on to contact the nun who had lodged an FIR alleging rape during the Orissa bandh on August 25.

Mishra said the government had already urged the church leaders to cooperate with the police to carry forward investigation so that the culprits could be punished.

"But we have not received any response from anybody," he said.

The police had meanwhile searched the nun at her native village in Sambalpur district and another all-women team headed by IG rank officer B Radhika also failed to get any trace on the whereabouts of the nun.

"We are planning to send another team to Kerala [Images]," a senior home department official said, adding that the government had reiterated its appeal to the alleged victim to cooperate in investigation.

"We have assured the nun and others in the community of all kinds of security, if they come forward to cooperate in the investigation," DGP Manmohan Praharaj told PTI.

He said the police could make arrangements for speedy completion of investigation into the matter.

Praharaj said the Orissa police have arrested the main accused in the alleged case and they are waiting for the victim to identify him.

"We have nabbed the prime accused in the alleged nun rape case incident on Tuesday."

The main accused, identified as Somanath Pradhan of Rajaghar village under Baliguda police station in Kandhamal district, was picked up from his house on the basis of information collected by the police.

Superintendent of Police (crime branch) Yatindra Koyal said more arrests were likely to be made in the rape case very soon and the investigation was on the right track.

"All the five arrests made so far in the case were on the basis of concrete evidence available with us," he said.

The presence of the alleged victim was essential because the nun had reportedly told some private news channel that she could identify the accused.