Mo. Rev. Stat. § 115.191: Investigative authorization of election authority.

The election authority may investigate the residence or other qualifications of any voter at any time it deems necessary. The election authority shall investigate material affecting any voter's qualifications brought to its attention from any source, and such investigations shall be conducted in the manner it directs. The election authority may defer investigation of material brought to its attention within ten days of an election until after the election if it determines time does not permit an earlier investigation.