The Department of Homeland Security has launched a widespread investigation into the secret government surveillance of journalists and activists at the U.S. and Mexico border.

NBC 7 Investigates broke the story of the secret database in March after reviewing leaked documents from an anonymous source inside the DHS.

A letter from the Department of Homeland Security’s acting Inspector General, Jennifer Costello, released by a group of Democratic senators who inquired about the program, said “criminal investigators, program analysts, and attorneys” are now conducting an investigation into the secret database and will release those findings publicly.

The documents obtained by NBC 7, showed the Trump Administration compiled a database of attorneys, immigration advocates, journalists who were affiliated with or covering the 2018 surge of thousands of migrants traveling from Central America to the U.S to seek asylum.

The intelligence gathering efforts were done under the directives of “Operation Secure Line,” a Department of Defense initiative to address increased border crossings as a result of the migrant caravan.

The list of surveillance targets included 10 journalists, three attorneys, and 46 others who the agents classified as organizers, or instigators associated with the caravan. Members of organizations such as Border Angels, Pueblo Sin Fronteras, and Al Otro Lado were also tracked.

In May, U.S. Senators Elizabeth Warren, Tom Udall, Richard Blumenthal, and Kamala Harris requested the Department of Homeland Security respond to “serious concerns” over the constitutionality of the surveillance program and asked for additional information on the directives and goals of the program.

Acting Inspector General Costello responded on July 15, stating the department had launched an investigation.

“We plan to review the leaked...document in order to determine why it was created, what it is used for, and what happened to the people named in it,” reads Costello’s letter. “We also anticipate reviewing other specific allegations of targeting and/or harassment of lawyers, journalists, and advocates and evaluate whether [Customs and Border Protection’s] actions complied with law and policy.”

The Senators all agreed an investigation was warranted.

“I’m glad that the DHS Office of Inspector General is opening an investigation into the CBP’s alarming surveillance reportedly targeting journalists, attorneys, and organizers,” stated presidential candidate and U.S. Senator, Elizabeth Warren. ”The American public deserves answers about how and why DHS obtained this information and how DHS officials and law enforcement agencies have used it.”

Senator Blumenthal had harsher language for President Trump.

“Putting journalists, attorneys, and activists on a secret government watch list may be a favorite move of one of President Trump’s autocratic friends, but it is not a tactic we should tolerate in our democracy,” said Blumenthal.