TPM story quotes the sheriff’s statement:

Voters in Hinds County can rest assured that there wasn’t a breach of security as it relates to the integrity of the voting process. All voting ballots were placed in a secured vault inside of the Hinds County Circuit Clerk’s Office, which was also locked during the time these individuals were in the building.

These individuals only had access to the common areas of the courthouse, which includes the hallways, and restroom area.