What would it take to use City Hall as a refuge for immigrants?

Boston City Hall.Keith Bedford/Globe Staff/File 2016

City officials met Thursday to work out logistics in the event they decide to provide what Mayor Martin J. Walsh is calling “emergency shelter” to undocumented immigrants as “a last resort” type of measure against President Trump’s immigration crackdown.

Among other things, they discussed sleeping arrangements, restroom facilities, and security, and planned to hold more meetings. They also considered the possibility of accommodating immigrants from outside the city who might want a refuge in Boston, city officials said.

Thursday’s meeting took place one day after Walsh offered to open City Hall, if needed, to unauthorized immigrants, after Trump signed an executive order to dramatically crack down on illegal immigrants, triggering fear among many groups in Boston and the nation.

Walsh offered City Hall “if people want to live here,’’ saying he won’t back down in the face of Trump’s policies. Boston is one of several Massachusetts municipalities that do not actively work with US authorities to deport most undocumented immigrants — a so-called sanctuary city.

“I offered City Hall for last resort shelter and protection for those unjustly targeted by [Trump’s] recent executive orders,’’ Walsh said in a statement. “I’m hoping my efforts and the efforts of others will lead us to a much more desirable outcome.”

But after his pronouncement on Wednesday, it was not immediately clear how the mayor would carry out his promise. Where exactly would immigrants stay in City Hall? The cavernous mezzanine? How would it work?

A former state representative, Alice Wolf of Cambridge — which became a sanctuary city in 1985 — said she doesn’t know of any city halls serving as shelters for immigrants. The Globe could not find one, either. Wolf led Cambridge’s sanctuary effort after officials learned of the plight of several Salvadoran refugees who fled civil war in their homeland and took refuge in the old Cambridge Baptist Church. Councilors were outraged that the federal government would not grant them asylum, Wolf said.

“We are in a different political climate [now], and we don’t know what to expect” of the Trump administration, Wolf said. “So I applaud people [like Walsh] who want to take steps that will protect people who are really at risk.”

Walsh’s words of defiance were praised by members of Boston’s immigrant community, who said he offered a shield against Trump’s policies. But Iván Espinoza-Madrigal, executive director of the Lawyers’ Committee for Civil Rights and Economic Justice, wondered if the mayor and his administration would be able to move beyond rhetoric to specific policies that would really affect the lives of immigrant residents.

He said the Walsh administration has been slow to address key issues such as developing anti-registration policies that would prevent government officials from tracking immigrant groups, including Muslims. Nor has the city been quick to grant municipal ID cards to those unable to get driver’s licenses or other government identification.

New York City began a municipal ID program in 2015 under the administration of Mayor Bill de Blasio, who like Walsh is serving his first term.

On Monday, the Walsh administration announced it was seeking bids to study the feasibility of a city ID program.

“We are still assessing the viability of a program that has clearly worked in New Haven, in San Francisco, in New York, and in many other cities,” Espinoza-Madrigal said. “There is unnecessary red tape and delay for a measure that has a track record of success in other cities.’’