Former Maharashtra Home Minister Anil Deshmukh - who resigned last week on "moral grounds" over corruption allegations - has been summoned by the CBI for questioning on Wednesday.
The summons comes days after the Supreme Court refused a plea from the state government and Mr Deshmukh to intervene in a Bombay High Court order that approved a 15-day 'preliminary inquiry' by the CBI into charges levelled by ex-Mumbai police chief Param Bir Singh.
The top court said the allegations were "extremely serious", and that an independent probe was warranted since both Mr Deshmukh and Mr Singh occupied prominent public posts.
The CBI has already questioned two personal staffers of Mr Deshmukh, including Sanjeev Palande, who Mr Singh said was present when the ex-Home Minister outlined his extortion racket. The two appeared before the agency's office in Mumbai's Santacruz on Sunday, news agency PTI reported.
The agency has also spoken to controversial police officer Sachin Waze - who is in NIA custody in connection with the Mukesh Ambani bomb scare and murder of auto parts dealer Mansukh Hiran.
According to Mr Singh, who was questioned earlier this week, Mr Waze - whose return to the police force after 16 years was allegedly pushed through by Mr Singh - was one of the officers directed by Mr Deshmukh to extort Rs 100 crore per month from Mumbai bars and restaurants.
He has also alleged corruption with reference to police transfers and postings.
Mr Deshmukh and his party, the Nationalist Congress Party (NCP), have denied all accusations; they say the charges are an attempt by Mr Singh - transferred to the Home Guards over "unforgivable" lapses in the Ambani bomb scare case - to divert attention from his predicament.
Last month party chief Mr Pawar said: "The timing of these allegations... has to be looked into. Why now? Param Bir Singh has made these allegations after he was transferred."
The row over Mr Deshmukh's alleged corruption exploded after Param Bir Singh's letter to Chief Minister Uddhav Thackeray, in which he detailed his claims. It quickly spiraled into a political stand-off, with the opposition BJP gunning for the ruling alliance led by ex-allies Shiv Sena.
With input from PTI
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