Led by state Law Minister Chandrima Bhattacharya, the supporters squatted in front of the office buildings holding placards and shouting slogans.
Bhattacharya told reporters, "The CBI was intentionally trying to divert the course of the probe with a political motivation under the influence of Narendra Modi-led BJP government at the Centre."
She alleged, "The CBI is trying the defame our Chief Minister Mamata Banerjee and the party. The way the probe is being done is not legally tenable." The people of the state would never accept such things, she said.
The agency questioned the party's Rajya Sabha MP Srinjoy Bose yesterday for almost eight hours. Others owing allegiance to the Trinamool Congress were also grilled by the agency.
Trinamool Congress has suspended party MP Kunal Ghosh who is behind bars.