The Tamil Nadu Police sent mobile phones confiscated from the four persons arrested in connection with the Pollachi sexual assault case, for analysis in an effort to gather more details, a police official told a news agency.
The Coimbatore (Rural) Police believe that the network of criminals will be about 15 members and are currently probing it.
Pollachi, a town in Coimbatore district, is about 535 km from Chennai. The four accused -- Thirunavukkarasu, Sabarirajan, Vasanthakumar, Satish -- were arrested in connection with the crime.
According to the police, the accused would befriend women on social media first. After gaining the girl's confidence, she would be invited to a secluded place and sexually assaulted which was also videographed.
Later the victims were blackmailed for money or for physical submission.
With opposition parties claiming that the ruling AIADMK was trying to shield its members alleged to have been involved in the crime, the party on Monday expelled worker A Nagaraj for assaulting a victim's brother.
Meanwhile, V Jayaraman, deputy speaker of the Tamil Nadu Assembly, told the media that opposition parties were trying to spread rumours to tarnish his name by linking his family members to the alleged crime.
Thirunavukkarasu, when he was in hiding, released a video saying politicians were also involved and wanted the case to be transferred to the Central Bureau of Investigation (CBI).
Although the Tamil Nadu government gave its nod for a CBI probe into the Pollachi sexual assault-cum-blackmail case, security was heightened and holidays declared in colleges across Chennai with stirs gaining momentum as more awful facts of the abuse came out.
All colleges were shut down in the town, 535 km from the state capital, by the authorities following student protests, demanding action against the culprits now in custody.
Stringent security has been put in place ever since details of how scores of women from college teachers to students even working professionals and others were sexually assaulted, harassed and blackmailed by the gang came to light.
Videos surfaced apparently show victims being lured to secluded spots and molested, filmed in the process, and blackmailed for money.
On Wednesday, the Madras High Court even rapped the media for poor coverage of the huge crime that was being committed over days.
The AIADMK government decided to hand over the investigation to the CBI, soon after the probe was transferred to the Crime Branch-Crime Investigation Department (CBCID) from the Coimbatore police, said an official.
The government's move came as the probe involves analysis of mobile phones, social media posts of the four accused and the affected women.
It was not even 24 hours that the CBCID started its probe into the crime taking over from the Coimbatore police.
The CBCID even formed a special team to start the probe as "the number of people involved in the crime was yet to be known" one of the investigators said.
Tamil Nadu Director General of Police T.K. Rajendran had ordered the transfer to the CBCID only on Tuesday.
The case made national headlines after the high court rap and huge protests by students, and women groups on social media.