Former Mumbai police commissioner Param Bir Singh today appeared before the police officials in Thane, Maharashtra, in connection with the investigation into an extortion case registered against him there, sources said.Param Bir Singh reached the Thane Nagar police station along with his lawyer around 10.30 am, they said.The probe team is likely to record his statement, the sources said, adding that zonal DCP Avinash Ambure was present at the police station to supervise the probe.The Thane Nagar police had registered the case of extortion against Singh and others based on a complaint lodged by builder and bookie Ketan Tanna, 54, in July this year.In the complaint, Ketan Tanna alleged that when Singh was the police commissioner of Thane between 2018 and 2019, he and other accused had extorted Rs 1.25 crore from him and that he was also threatened of dire consequences. As per the complaint, the accused had also extorted Rs 3 crore from Ketan Tanna's friend Sonu Jalan in a similar manner.A non-bailable warrant was issued against Param Bir Singh in connection with this case.Apart from Param Bir Singh, retired inspector Pradeep Sharma, inspector Rajkumar Kothmire and DCP Deepak Devraj are some of the accused in the case.Two accused have been arrested in the case so far with one of them was getting bail by a court a couple of days back.Param Bir Singh is facing a total of five extortion cases in Maharashtra, two of them in Thane. The Thane police have formed a special investigation team (SIT) to probe these two extortion cases.Param Bir Singh, who was recently declared an absconder by a court, arrived in Mumbai on Thursday after remaining incommunicado for several months. After his arrival, he was questioned for seven hours by the Mumbai police's crime branch in a separate extortion case.He was removed as Mumbai's top cop earlier this year after police officer Sachin Waze was arrested in the case of an SUV with explosives found near industrialist Mukesh Ambani's house, Antilia, and the subsequent suspicious death of businessman Mansukh Hiran. The Supreme Court granted Param Bir Singh protection from arrest a few days ago.