A mother and her teenage daughter were allegedly gang-raped in a field after being dragged from their car outside New Delhi, police said on Sunday, India's latest brutal sexual attack.
A gang of robbers allegedly stopped the family's car along a busy highway early on Saturday, said additional director general of police Daljeet Chaudhary.
The mother has told officers that she and her 14-year-old daughter were pulled from the vehicle and raped by six men.
The family's four male members have said they were tied up with ropes and their belongings stolen while the attack took place, Chaudhary told AFP.
Police detained 16 people on Sunday and were still searching for the main suspect in the attack, which took place in Uttar Pradesh state, about 65 kilometres (40 miles) south of the capital.
"The main suspect has been identified. We are trying to arrest him as soon as possible and send him to jail under stringent sections of the law," Chaudhary said.
India toughened punishments for rapists following the fatal gang rape of a student in Delhi in 2012 that shone a global spotlight on frightening levels of violence against women in the country.
But rape and sexual assault occur regularly, with attacks hitting the headlines on an almost daily basis.
The most recent official figures show 36,735 rapes were reported across the country in 2014. But activists say the true number is likely much higher as many women do not speak out because of the social stigma attached to sexual crimes.