RALEIGH (AP) — A federal North Carolina prosecutor’s office that has been investigating allegations of voter-related fraud said on Friday that 24 more people have been charged over the past 18 months.

Two of the defendants were charged earlier this year with unlawful voting in the 2016 general election, a news release from the U.S. Attorney’s Office for eastern North Carolina said.

More than 15 other defendants, including four whose indictments were unsealed Friday, were charged with falsely claiming U.S. citizenship to register to vote, according to a list the government released of those charged and their nationalities. The two charged with unlawful voting also are accused of false claims of citizenship.

Several people also have been charged with naturalization fraud and the misuse of immigration visas and other documents.

Those charged are listed as being from Mexico and several central American countries, as well as from France, Yemen, Iraq and Nigeria and other countries. Each defendant was charged individually, and there are no conspiracy charges, according to the news release.

The first charges were filed in September 2019 and arrests have continued into this month, according to information provided by prosecutors. The defendants face possible prison time and fines.

In August 2018, the U.S. attorney in Raleigh announced charges against 19 non-U.S. citizens, accusing them of illegally voting in the 2016 election. Prosecutors at the time said the investigation into voting fraud was ongoing.

Soon after, it became public that then-U.S. Attorney Bobby Higdon employed subpoenas issued on behalf of Immigration and Customs Enforcement in order to try to obtain voting records from the North Carolina elections board and more than 40 county boards.

The state board took issue with the requests, calling them overly broad and unreasonable. The board estimated the subpoenas covered over 20 million records. Voting rights activists worried the records were a fishing expedition before midterm elections.

The board said in early 2019 it would provide records for nearly 300 people previously registered to vote in eastern North Carolina and for another 500 people outside the region. It wasn’t clear if these records contributed to cases against new defendants.

Higdon, who was nominated by then-President Donald Trump to the prosecutor’s post, resigned in late February as President Joe Biden requested U.S. attorneys step down. The Raleigh office is now led by an interim top prosecutor.