Who carries out investigation for election-related criminal offenses?

Pakistan
Representation of the People Act, 1976
93. Certain Powers of a1[Police Officer].—A Police Officer may—
(a) arrest without warrant,notwithstanding anything contained in the Code of Criminal Procedure, 1898 (ActV. of 1898), any person—
(i) who, commits personationor an offence under section 86 if the Presiding Officer directs him to soarrest such person;
(ii) who, being removed fromthe polling station by the Presiding Officer under section 32 commits anyoffence at the polling station.
(b) remove any notice, sign,banner or flag used in contravention of section 85; and
(c) seize any instrument orapparatus used in contravention of section 86 and take such steps, includinguse of force, as may be reasonable necessary for preventing such contravention.
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