A protest held by the opposition DMK in Pollachi on Tuesday, March 13. (Photo: DMK)

A sexual abuse case uncovered in the western Tamil town of Pollachi has appalled netizens and given the opposition ammunition ahead of the general election in April and May.

Thousands of students protested in Tamil Nadu on Wednesday, according to local channels, as investigators continued to look into a gang's alleged sexual crimes against multiple women.

How did the case come to light?

On February 24, a young woman complained to the police that four men had tried to disrobe her in a car and filmed the assault.

There is a video that shows the woman, 19, screaming and resisting her attackers.

The four men -- Thirunavakkarasu, Sathish, Sabariraj and Vasanthkumar -- have been arrested.

What is the scale of the gang's alleged crimes?

Two police officials who spoke to India Today TV said the four men sexually harassed dozens of women -- over 50 of them -- for over two years across Tamil Nadu. Among them were teachers and students from schools and colleges.

The officials described a chilling pattern. The men, they said, found victims on Facebook and forced them to meet in person after befriending them. They then harassed them in moving vehicles, hotels or farmhouses.

Most of the victims refused to make formal complaints, the police officials said.

The police say they have retrieved videos from the gang that show sexual harassment or assault.

In a letter to Tamil Nadu's police chief, the National Commission for Women has called for "appropriate action" and asked for a report.

#MeToo India's official Twitter account (@IndiaMeToo) has been tracking developments in the case.

What action has been taken?

Thirunavakkarasu, Sathish, Sabariraj and Vasanthkumar have been booked under sections of the Indian Penal Code and two other laws -- the Tamil Nadu Prohibition of Harassment of Women Act and the Goondas Act.

The case has been transferred to the Crime Branch CID. The police have said the investigation will be headed by CB-CID Superintendent of Police Nisha Parthipan, and that the public can submit proof.

Although the Tamil Nadu government has recommended that the CBI take over, activists, students and political parties want a judicial probe.

How has the case acquired a political colour?

Opposition parties were outraged when a local functionary from the ruling AIADMK allegedly attacked the brother of the victim along with other members of the gang under the scanner.

He and three others were arrested for this attack. The AIADMK expelled him.

The Communist Party of India's state secretary has alleged that people suspect members of AIADMK were supporting the suspects.

"Even after the media brought this to light, and after Opposition parties -- including the DMK -- protested, why has no appropriate action been taken?" - MK Stalin, Leader of the Opposition, on March 11, 2019

V Jayaraman, an AIADMK MLA, has denied that his family is involved in the case (in response to newspaper reports), and accused DMK chief MK Stalin's son-in-law of instigating the controversy. Jayaraman also claimed that a DMK district secretary's son was a close friend of one of the suspects.

The victim's relatives, including her brother, have asked parties not to politicise the case.

Where is Pollachi?

Pollachi is located around 535 km from Chennai in Tamil Nadu's Coimbatore district, not far from the state's border with Kerala.

Inputs from Lokpria Vasudevan, Shalini Lobo and agencies