Workers at an unmarked building suspected of housing migrants in Tuscon, Ariz. refused to answer Fox News' Rachel Campos-Duffy's questions and asked her to leave the facility, she reported Monday.

The "Fox & Friends Weekend" host received a tip to investigate the facility Casa Alitas, which had all signs removed from its exterior. She explained the lack of signs was a signal it was an NGO — non-governmental organization — housing illegal immigrants.

After asking if she could book a room, a woman behind the hotel counter asked Campos-Duffy to leave the building, claiming she was on "private property." 

The woman refused to answer questions about whose property it was, instead asking security to escort Campos-Duffy out of the building. 

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screencap of Fox News report investigating Tucson migrant facility

"Fox & Friends Weekend" host Rachel Campos-Duffy investigated a migrant shelter in Tucson, Arizona. (Fox News)

"Is this where illegals are being housed with government funding?" Campos-Duffy asked as an elderly security guard came out to escort her.

The woman demanded the Fox News crew leave the property and threatened to call the police.

"Please call them," Campos-Duffy responded.

Another young woman who came out also pressured the crew to leave. She covered up her name tag after Campos-Duffy identified the shelter listed as "Casa Alitas" on her badge.

"This is an NGO paid for by government money," Campos-Duffy said. 

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screencap of Fox news report on Tucson migrant shelter

Workers at an unmarked migrant facility in Tucson, Arizona refused to answer questions about the shelter to Fox News. (Fox News)

The worker refused to answer questions about what the organization did.

"Why so much secrecy? That's what the American people want to understand. Why?" Campos-Duffy pressed.

The woman ushered the news crew out of the building, repeating, "You guys cannot come into our shelter."

The report is part of a larger Fox News investigation into places being used to house illegal immigrants across the country.

Illegal border crossings are now primarily happening in Arizona and California, according to data from the U.S. Customs and Border Protection.

In December, Democratic Arizona Gov. Katie Hobbs deployed the state's national guard to deal with a surge of migrants at its border with Mexico. 

The Tucson Sector has been particularly hard hit by a new wave of migrants coming over the border. The sector set a new record or weekly encounters when officials encountered over 17,500 migrants in one week.

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Casa Alitas' website describes itself as offering "shelter, necessities and travel assistance to asylum seeking families. Our guests arrive for a short stay, after their release from Border Patrol and ICE detention."

"Casa Alitas is a program of Catholic Community Services of Southern Arizona," the website states. "The Casa Alitas Leadership Team and Volunteer Service Coordinators support a network of paid staff, volunteers, and interns to create a safe, just, and compassionate refuge for the migrant families transiting through our Southern Arizona border communities. The Casa Alitas program is sustained by an inter-denominational network of faith collaborators and inter-organizational partnerships with federal, state, and municipal government agencies; universities and colleges; and other non-governmental organizations."

Fox News' Adam Shaw contributed to this report.