Two men have been arrested in Patna, in north-east India, after a video allegedly showing a woman being raped next to the holy River Ganges was shared widely on social media.
Police say the men took turns to assault the victim and film it.
The woman was reportedly dragged from the Ganges, where she had been bathing on Sunday morning.
In the video, she can be heard asking the men to consider the "sanctity" of the river, revered within Hinduism.
She also refers to it as "mother" - a term of affection and respect for the site.
Police said on Wednesday the mobile phone used to film the alleged assault had been seized and would be sent to a forensic laboratory for analysis, the Times of India reports.
Accounts conflict on how authorities learned of the incident - with police saying they only found out about it after seeing the clip online.
Other local reports suggest the woman had been earlier turned away from a police station after trying to come forward.
"She had completely suppressed the ordeal faced on Sunday and told no-one," rural superintendent Anand Kumar said on Wednesday.
"The matter surfaced only after the video became viral on Tuesday afternoon."
Mr Kumar said the woman, who is said to live in the same village as the suspects, then had to be persuaded to give a statement.
According to crime statistics, a woman is raped in India about every 13 minutes - but many more incidents are believed to go unreported because of the stigma still attached to rape and sexual assault.
Scrutiny of sexual violence has grown in India since the 2012 gang rape and murder of a 23-year-old student on a bus in the capital Delhi.
It sparked days of protests and forced the government to introduce tougher anti-rape laws, including the death penalty.
This year has seen the issue become a political flashpoint again, after a string of high-profile attacks against children.