It has been alleged that the state ruling party leaders played key role in stopping CBI from performing its legal duty after arresting four leaders on May 17 in the case.
Three agitators were picked up from Kidderpore area, while one was held in Beniapukur locality, a senior officer said.
They were taken to the state-run SSKM Hospital as both the politicians complained of breathlessness, an official said.
Narada row: Kolkata High Court stays bail order of two Trinamool ministers, Bengal MLA; Opposition hits out at Modi government
The High Court said it would hear the matter on Wednesday and till then the four accused will be in judicial custody.
The central agency arrested Trinamool Congress leaders Firhad Hakim, Subrata Mukherjee and Madan Mitra as well as former party leader Sovan Chatterjee in Kolkata in connection with the case.
Senior TMC leader and MLA Madan Mitra and former minister Sovan Chatterjee were also brought to Nizam Palace as part of the CBI probe, officials said.
The one time second-in-command of Trinamool, Roy's name figures in both the Saradha ponzi scam and Narada sting cases.