The Trump administration on Friday announced a major expansion of its denaturalization campaign targeting foreign-born American citizens accused of fraudulently obtaining U.S. citizenship.

The Justice Department unveiled denaturalization cases in federal courts across the country against roughly a dozen U.S. citizens born overseas. Officials said they had committed serious crimes or immigration fraud, or had ties to terrorism.

The announcement represents a dramatic increase in the federal government’s use of denaturalization, a lengthy and complicated legal procedure that has rarely been invoked by prior administrations. Between 1990 and 2017, for example, the U.S. government filed just over 300 denaturalization cases — or an average of 11 per year.

The group of naturalized U.S. citizens whose citizenship the Justice Department is now seeking to revoke includes immigrants from Bolivia, China, Colombia, Gambia, India, Iraq, Kenya, Morocco, Nigeria, Somalia and Uzbekistan.

Among those targeted by the denaturalization crackdown are a Colombian-born Catholic priest convicted of sexually assaulting a minor; a man born in Morocco with alleged ties to al Qaeda; a Somali immigrant who pleaded guilty to providing material support to al Shabaab, a U.S.-designated terrorist group; and a former Gambian police officer allegedly involved in war crimes.

The group also includes individuals who allegedly used false identities to apply for immigration benefits and a man who allegedly entered into sham marriages to commit immigration fraud.

In a separate announcement Friday, the Justice Department said it was also seeking to denaturalize Manuel Rocha, a former American diplomat who admitted to being a Cuban spy as part of a high-profile criminal case.

The denaturalization process involves Justice Department lawyers filing civil or criminal cases in federal courts and trying to convince judges that someone’s citizenship should be terminated. U.S. law allows denaturalization to occur when the government proves that a naturalized citizen obtained their citizenship illegally or through fraud, such as by concealing information on their immigration applications.

Those whose citizenship is revoked lose all the legal benefits that come with being an American citizen and return to their previous legal status, typically as permanent residents, who are deportable based on certain criminal conduct and other grounds.

In an interview with CBS News earlier this week, Acting Attorney General Todd Blanche previewed the administration’s denaturalization push, saying he believes there are “a lot of individuals who are citizens who shouldn’t be.”

Asked about concerns among some of the roughly 24 million naturalized citizens in the U.S., Blanche said only “a very small percentage” should be worried about the administration’s denaturalization efforts. Those who did not illegally obtain their citizenship, he said, don’t “have anything to worry about.”

“We should disincentivize people from committing fraud when they’re going to become a citizen of this great country,” Blanche said. “It is a drastic consequence of committing a fraud to get citizenship, just like it is a drastic action to commit fraud to get citizenship.”