With the fresh arrest, the total number of arrests in the sensational incident had mounted to eight. A police team which had gone to Kerala in search of the nun, accidentally came across the youths and arrested them.
"We are yet to ascertain the motive behind the youths' visit to Kerala," Inspector General of Police (Crime) Arun Ray said, adding that the accused youths were being brought to Orissa by the police team.
The police was also not sure whether the youths belonged to Kandhamal district or some other parts of the state.
"The surnames of the trio suggested that they might be from the coastal region of the state and not from Kandhamal," a senior official said, adding that the details of them would be available soon.
The 29-year-old nun was allegedly raped at K Nuagaon village under Baliguda police station area in Kandhamal district on August 25 during Orissa bandh, two days after violence erupted in the district in the aftermath of VHP leader Swami Laxamananda Saraswati's killing.
Meanwhile, the state government had placed a police inspector under suspension on charge of delaying investigation into the sensational case.
The alleged victim had lodged a written complaint with the police on August 26 and had also undergone medical examination.