The attack happened Tuesday night in a village in Uttar Pradesh state's Budaun district, said R.K.S. Rathore, a deputy inspector-general of police.
The victims were cousins, ages 14 and 16, and from the same village. They both belonged to what the police official called "backward castes," meaning they'd been born low on India's caste system that has long defined a person's place in society.
The girls' families filed a complaint accusing three brothers of rape and murder, Rathore told CNN.
"We are investigating all possible angles and collecting evidence," he said Thursday. "So far, we have no evidence that points to any kind of enmity."
Police have been able to arrest and charge at least one of the suspects in the case as they hunt for the others.
A police constable has also been arrested over allegations that he sided with the suspects and delayed the registration of the case.
This Uttar Pradesh incident is the latest of several rapes in India that have recently captured the world's attention.
Twitter was full of condemnations and anger about this case and the prevalence of rape in India. One called the incident "disgusting," another said she was "speechless," and many posed questions along the lines of, "When is India going to change?"
After all, India has been called out for its high incidence of rape before. Some suggest that the widely reported estimate of a rape being reported every 22 minutes, attributed to India's National Crime Records Bureau, is too low, because many females may not speak out or call out their assailants in what is in many respects still a male-dominated society.
The case credited with putting this situation on the world's radar took place in New Delhi in December 2012.
Then and there, a 23-year-old physiotherapy student was on a bus heading back from a movie with a male friend. Police said the driver and at least five other drunk men dragged her to the back of the bus and beat up her friend.
The men then took turns raping the woman, according to police, using an iron rod to violate her as the bus drove around the city for almost an hour. When they were done, they dumped the victims by the side of the road; the woman died from her injuries two weeks later at a hospital in Singapore.
That incident energized activists and women generally, with government officials promising action to ensure that girls and women feel safe.
A public opinion poll earlier this spring found that more than 90% of respondents think combating violence against women should be a priority, second only to corruption.
Yet the same MDRA/Avaaz survey found that 75% of those Indians participating in the country's recent election believe that political promises made to advocate women's rights have been inadequate so far.
Source: cnn.com By Harmeet Shah Singh and Greg Botelho, CNN