As the incoming Trump administration promises the mass deportation of unauthorized immigrants, federal authorities are eyeing California for a new detention facility for migrant adults.

U.S. Immigration and Customs Enforcement officials are looking for space to accommodate 850 to 950 people and focused on areas within two hours of its San Francisco regional field offices, which include outposts in Sacramento, San Jose and Bakersfield, according to a federal document seeking leads on possible locations.

CalMatters first reported ICE’s interest in opening a new center.

The agency’s desire to expand its immigration lockups predates Trump’s election. Officials began collecting information in August, about a month after President Biden toughened policies for asylum seekers at the Mexican border. In addition to California, ICE is looking into the possibility of new detention centers near Phoenix, El Paso and Seattle, according to the document asking for leads on locations.

“ICE has identified a need for immigration detention services within the Western U.S. area of responsibility,” an agency spokesman, Richard Beam, told CalMatters.

The contemplated centers would add about 3,800 available beds — an increase of about 10% over the current number of detainees — and house both adult men and women of various security classifications from low to high, according to ICE. The agency said it was open to publicly or privately owned sites and locations where other types of inmates are currently incarcerated, which could include county jails or for-profit prisons.

The half-dozen existing ICE detention facilities in the state are run by private companies.

President-elect Donald Trump has promised to launch the largest deportation operation in U.S. history, though how he plans to carry out or pay for it remains to be seen. More than 11 million unauthorized immigrants are believed to be living in the U.S. with only about 38,000 individuals in ICE detention, according to the agency website.

Elected officials in California are gearing up to fight the Trump administration over migrant roundups. Atty. Gen. Rob Bonta reminded public institutions last week of a state law limiting the cooperation of courthouses, hospitals, schools, universities and shelters with federal immigration enforcement efforts.

“No matter who is in the White House, in California, we will continue to lead with California values,” Bonta said in a statement. “We cannot let the Trump deportation machine create a culture of fear and mistrust that prevents immigrants from accessing vital public services.”