YouTuber Dhruv Rathee, who was detained by Delhi Police ahead of the Cockroach Janta Party's (CJP) protest at Jantar Mantar, was released late on Saturday night, an official said on Sunday.
"He can be detained again, or further legal action might be taken if he tries to go to Jantar Mantar despite prohibitory orders," a police source said.
Rathee was detained from his residence in Gurugram's Sector 56 on Saturday as police stepped up security across the national capital to prevent protesters from reaching Jantar Mantar for a demonstration demanding the resignation of Chief Election Commissioner Gyanesh Kumar over alleged irregularities related to the SIR.
The detention came amid an unprecedented security clampdown in Delhi, where more than 7,000 protesters were detained at multiple locations, police sources said.
Several opposition leaders, including former chief ministers Arvind Kejriwal, Mamata Banerjee, Pinarayi Vijayan and Manik Sarkar, were also detained while attempting to join the protest.
CJP leaders Abhijeet Dipke, Ashutosh Ranka and Saurav Das have been placed under preventive arrest after their detention from the airport.
Police are likely to register multiple FIRs in connection with the alleged assaults on personnel during the protest, a senior officer said.