Delhi Police with the help of state's special task force and district police arrested Pradeep Ram, between 20 and 25 years old from Badhaiya area, Bihar Director General of Police Abhayanand said in Patna.
"Pradeep was presented in the court of the chief judicial magistrate in Lakhisarai and the court granted a three-day transit remand (of Pradeep) to the Delhi Police," Lakhisarai Superintendent of Police Rajeev Mishra said.
Additional Director General of Police (headquarters) Ravinder Kumar said that in view of prevailing anger among the people, Pradeep was being taken to Patna under tight security, and from there he will be taken to Delhi.
Police sources said that the prime accused in the case, 22-year-old Manoj Kumar, from whose room in Delhi the girl was recovered days after she went missing April 15, had blamed Pradeep for the brutal attack on the girl.
"Manoj said he met Pradeep on a train. The two were casual labourers who would often meet for a drink," a police official told IANS in New Delhi.
Police said Manoj had admitted that on the day of the incident the two had been drinking, and struck up the idea of finding a girl. When they came out of their room, they saw the five-year-old at her games. Manoj said he lured the girl with chocolate, but blamed Pradeep for the rape.
"We will interrogate Pradeep to learn if what Manoj said is true," the police official said.
Manoj Kumar, the prime accused, was held from Bihar's Mujaffarpur district Saturday, where he was hiding at the home of his parents-in-law.
He was sent to judicial custody Sunday till May 4, following his interrogation by Delhi Police.
The minor victim is undergoing treatment at All India Institute of Medical Sciences (AIIMS) in New Delhi.