The special investigation team (SIT) of Odisha Police probing the kidnap and murder of a five-year-old in Nayagarh district Monday said the girl was a victim of sexual assault and murder.
The victim's mother has demanded a CBI inquiry into the case.
In the first arrest in the case, a college student was booked on Sunday from Jadupur village, where the victim's family also stays, in connection with the case.
SIT chief Arun Bothra said on Monday that there is sufficient evidence against the college student who is the prime accused in the case and has been interrogated by Nayagarh police.
"We arrested the youth after getting required evidence against him. Sexual assault was the motive behind killing of the little girl," Bothra told reporters.
The accused was produced at a POCSO court in Nayagarh Monday which allowed the SIT to take him on remand till December 24.
Rejecting the claims of innocence made by the student and his family, he said the youth was interrogated a number of times in the last ten days before his arrest.
"The involvement of any of his associates in the case is still under investigation, Bothra said.
The youth was absconding for the past five months since the girl went missing, he said.
The crime branch of Odisha Police had said in a press release on Sunday that a person had been arrested in connection with the case under sections of the IPC and the POCSO Act.
The youths mother has claimed that he is innocent and the girl's parents have doubted the SIT's findings.
The police arrested a village youth and not the persons who were involved as they are close to the minister. The case should be handed over to the CBI, the girls mother, who has been sitting on dharna in front of Nayagarh district collectors office along with BJP activists, said.
The minor girl had gone missing while playing near her house on July 14 and her skeletal remains were found in a gunny bag in the backside of her house in Jadupur village on July 23.
The incident came to light after her parents attempted self-immolation in front of the state assembly in Bhubaneswar on November 24. The state government recently ordered a high court-monitored SIT investigation after the issue rocked the assembly for several days.
The opposition BJP has been demanding a CBI probe and dismissal of Agriculture Minister Arun Kumar Sahoo charging him with shielding the prime accused in the crime.
The saffron party on Sunday launched a five-day-long march from Bhubaneswar to Nayagarh demanding justice for the victim''s family.
Leader of Opposition Pradipta Naik of BJP Monday joined the padayatra on its second day and sought clarification from the state government on the fate of about 5,000 minor children missing from the state since two years.
The opposition Congress activists also staged dharnas in front of the offices of the district police superintendents protesting against increasing crimes against children and women.