Police identified the inmate as Amit Shukla. He is one of the accused in the murder of TV journalist Soumya Viswanathan.
The probe will establish how a mobile phone was smuggled inside Tihar Jail and handed to an inmate. It will also be checked how calls were made despite jammers in place at the jail.
Director General (Prisons) Vimla Mehra said: “We will definitely order an inquiry into it.”
Police said Arun Kumar, a compounder who worked at the Tihar dispensary, had been arrested for allegedly collecting Rs 50,000 as the first instalment from a businessman who had been targeted by Shukla.
According to police, Kumar got to know Shukla during the four years he served as a compounder at the dispensary. The two struck a friendship and Shukla began to use him to collect the extortion money.
Police said they first received information that some gangsters lodged in Tihar Jail had been functioning from behind the bars.
It was discovered that Shukla had been calling one Rajender, a Vaishali resident, on his mobile phone to extort money.
On January 24, Rajender, who works as a manager at a businessman’s office, lodged a formal complaint about the threatening calls he had been receiving, police said. The case was transferred to the special cell on January 26. But a day earlier, Rajender, fearing for his life, handed Rs 50,000 as the first instalment of an extortion sum.
On January 27, police tracked down Kumar, who had allegedly collected the money on behalf of Shukla. He was arrested from Mukund Vihar.
Police claimed Shukla was once a member of a gang of extortionists who used to target businessmen in Uttar Pradesh, Mumbai and Delhi.
Special Commissioner of Police (Special Cell) S N Srivastava said, “We are yet to interrogate Amit Shukla as he is presently inside Tihar Jail. Once we interrogate him, we will get more details on who all are behind this extortion racket operating from inside the prison.”