In Leon County, Supervisor of Elections Mark Earley said two U.S. Customs and Border Protection vehicles were seen Monday at the Northeast Branch Library, the county’s busiest polling site. The vehicles remained for about 10 minutes and then left, Earley said. His office received no calls about the incident.

In Monroe County, Supervisor of Elections Sherri Hodies said she had opened an investigation after reports that masked federal agents conducted a stop at a polling place in Key Largo on Tuesday. Both supervisors said they had contacted the FBI.

Federal law bars armed federal agents from conducting activities in or near polling places, except when force is needed to repel armed enemies of the United States. U.S. Immigration and Customs Enforcement and the Florida Department of State, which oversees state elections, had not responded to requests for comment by Tuesday evening.

The reports came after the FBI reassured Florida election supervisors at a statewide elections conference that immigration enforcement would not take place at polling sites. Brevard County Supervisor of Elections Tim Bobanic said officials had repeatedly been told there were no plans for such activity in Florida.

Earley called the sighting in Leon County “very unfortunate” and said he would be surprised if it happened again. He said voters should not face intimidation from law enforcement or other government officials and urged anyone with questions or concerns to contact their local elections supervisor.

Thomas Kennedy, a spokesperson for the Florida Immigrant Coalition, said the presence of Border Patrol at polling places was unnecessary and could be perceived as an intimidation tactic. He said he had hoped it would not happen but expected the possibility.

The Monroe County investigation may help clarify what happened in Key Largo. In the meantime, the reports have renewed attention to how the presence of federal officers near voting locations could affect public confidence and voters’ ability to cast ballots without fear.