Sarvesh Yadav was taken into custody on Thursday for questioning. Pappu Yadav, an accused in the case, was arrested on Wednesday. The police are on the lookout for four other accused.
Bodies of the cousins, aged 14 and 15, were found hanging from a tree some 100 metres away from their home on Wednesday morning. The girls were missing since Tuesday night.
Hundreds of angry villagers stayed next to the tree after the bodies were found, silently protesting alleged police inaction in the case.
RKS Rathore, deputy inspector general (Bareilly range) told HT over phone on Thursday that a panel of three doctors including a lady doctor had confirmed sexual assault on the teenagers.
He said the panel had also found some ante-mortem injuries on the bodies, while the death was caused due to hanging.
Rathore added a police team had been formed to arrest the remaining accused. He also admitted that constable Sarvesh Yadav was taken into custody.
Sex crimes continue unabated in the country despite the government tightening anti-rape laws last year in the aftermath of the 16/12 incident, making gang rape punishable by death penalty even in cases where the victim survives.
Records show a rape is committed every 22 minutes in India, a nation of 1.2 billion people.