Homeland Security Secretary Kristi Noem defiantly defended the Trump administration’s hard-line immigration policies against fierce questioning by Democrats during a House committee hearing. Noem portrayed migrants as a major threat faced by the nation that justifies a crackdown that has seen widespread arrests, deportations and a dizzying pace of restrictions on foreigners.

Noem, who heads the agency central to President Donald Trump’s approach to immigration, received backup from Republicans on the panel but fierce questioning from Democrats who called for her resignation. The secretary's testimony was interrupted by protesters calling for an end to deportations.

Noem, who was testifying in front of the House Committee on Homeland Security to discuss “Worldwide Threats to the Homeland,” emphasized in her remarks how big a role she believed immigration played in those threats to the country. Her remarks, and the Democrats' questioning, focused heavily on the Trump administration's immigration policies, whereas in years past the hearing has centered on issues such as cybersecurity, terrorism, China and border security.

Trump returned to power in January with what he says is a mandate to reshape immigration in the U.S., claiming the country is under an invasion.

In the months since, the number of people in immigration detention has skyrocketed; the administration has continued to remove migrants to countries they are not from; and, in the wake of an Afghan national being accused of shooting two National Guard troops, Noem’s department has dramatically stepped up checks and screening of immigrants in the U.S.

Immigration enforcement operations, especially in Los Angeles and Chicago, have become increasingly contentious, with federal agents and activists frequently clashing over her department's tactics.

Noem's department is under particular scrutiny because Congress in July passed legislation giving it roughly $165 billion to carry out its mass deportations agenda and secure the border. The department is getting more money to hire 10,000 more deportation officers, complete the wall between the U.S. and Mexico and increase detention and removal of foreigners from the country.

The secretary's appearance also comes as a federal judge is investigating whether she should face a contempt charge over flights carrying migrants to El Salvador.