In his all-out war on illegal immigration, President Donald Trump has branded immigrants as “criminals,” “invaders” and “predators,” as his administration targets millions of Haitians, Latin Americans, gang members and foreign college students for deportation.

Now, the president has directed the Justice Department to bolster its resources in a major crackdown on naturalized citizens suspected of unlawfully obtaining their U.S. citizenship.

According to a recent memo, the department plans to focus not only on individuals who may have lied about a crime or having done something illegal during the naturalization process. But authorities also plan to focus on others who may have committed a crime after becoming citizens — a generally untested legal frontier.