When a Police suspects a person that he might commit a cognizable offence, then it can take such person under preventive arrest. No FIR or Warrant is required for such arrest as the Police is protected under Section 151 of Cr.P.C.

Decoding Sections 149 to 152 of Code of Criminal Procedure:

The Police Officer can intervene and prevent any person from being committing cognizable offence. Any Subordinate Police Officer who has acquainted with certain information of committing a cognizable offence shall immediately report to his Superior Officer or to the Officer concerned who is responsible to prevent such offence. A Police Officer who has come to know of a plan to commit a Cognizable Offence may arrest such person so plans without any Warrant of Arrest from the concerned Magistrate provided he has reason to believe that such things cannot be prevented without an arrest. Such arrested person should not be kept under custody for more than 24 hours unless such custody is authorised by the law under any of the provisions of the Code. The Police Officer on his own can intervene and prevent any damages or removal from being committing to any public property; movable or immovable including any public landmark or other things.

Also read PREVENTIVE ARREST BY POLICE – SECTIONS 41-60 OF CR.P.C. DECODED