Environmental activist S Mugilan is reported to have gone missing in Tamil Nadu hours after he addressed a press conference in Chennai on Friday during which he accused senior police officials of orchestrating violence in Thoothukudi during last year's anti-Sterlite protests, in which police firing killed at least 13 people. Human Rights Defenders Alert, a network for the protection of human rights activists, sent a missing person's complaint to the director general of police in Chennai on Sunday. The organisation's national working secretary, Henri Tiphagne, said a habeas corpus petition will be filed before the Madras High Court on Monday. At Friday's press conference, Mugilan alleged that the police, in connivance with the management of Sterlite, were behind the violence that took place on May 22. He specifically named Indian Police Service officers Shailesh Kumar Yadav and Kapil Kumar Saratkar. While Yadav was the Inspector General of Police of South Zone at the time of the incident, Saratkar was the Tirunelveli Deputy Inspector General of Police. Both were transferred out of the area in June. Several protestors in Thoothukudi were arrested on May 22 for rioting, burning vehicles in the premises of the collectorate, and for pelting stones and damaging public property. The police have not officially responded to Mugilan's allegations. Attempts by Scroll.in to contact the police on the phone for a response were not successful. Missing from train After the press conference, Mugilan is said to have met his colleague VP Ponnarasan and a few other friends in Chennai. At about 10.30 pm, Ponnarasan and Mugilan reached Egmore railway station. While Ponnarasan took the Mangalore Express to Karur, Mugilan boarded another train to Madurai. I Aseervatham, state coordinator of human rights organisation People's Watch, said Mugilan had called him on Friday evening and said he was boarding a train to Madurai and that he was expected to reach by 10.30 am the next day. Later that night, Mugilan spoke to his colleague Sridhar, who said the activist told him that he was travelling to Madurai in the Nagercoil Special. Mugilan also told Sridhar that he was apprehending some action by the police because he had exposed the role of higher police officers in the Thoothukudi violence and police firing. Aseervatham told Scroll.in that Mugilan never planned his trips so he travelled in an unreserved compartment. "He told me to file a police complaint in case he does not reach Madurai the next day," Aseervatham said. "His cell phone was active till 1.45 am on February 16 and lost connectivity from Olukkur in Villupuram district." In the complaint sent to the director general of police, Tiphagne said: "It is reasonably believed that Mugilan has been abducted from the train itself after he had alleged the role of higher police officers in the Thoothukudi police firing and the violence." Mugilan had alleged that Yadav and Saratkar were present at the District Collector's office prior to the violence that broke out there on May 22. He alleged that footage retrieved from CCTV cameras installed in the Collector's office showed the two senior police officials walk close to a pile of broken bricks and wooden planks in the office complex before the violence broke out. "Why did not he[Yadav] order the police to clear this?" Mugilan asked. In a press statement, Mugilan also alleged that the police had burnt the vehicles and blamed it on the anti-Sterlite protestors. He released a video titled Sterlite Hidden Truth, regarding the May 22 violence in Thoothukudi. The activist was booked for sedition in 2017. He was arrested in September that year for failing to appear before court despite being served summons related to protests against the Kudankulam nuclear plant. A case against him was registered nearly eight months later, in December last year.