As New York City officials scramble to find housing for an expected influx of migrants, the city is planning to house them in a stand-alone school gym in Coney Island, officials said Friday.

The city alerted the principal of P.S. 188 that the school’s gymnasium would be used as a sheltering site, said Ari Kagan, a Brooklyn councilman who represents the neighborhoods of Bensonhurst, Coney Island, Gravesend and Sea Gate.

“People are really concerned,” Mr. Kagan said Friday night. “I got a lot of phone calls from concerned parents, from community leaders. Nobody, nobody expressed their support for this plan.”

No migrants were being housed in the gym on Friday night, he said, but added: “What’s going to happen tomorrow and Sunday? Who knows?” He said that the city’s Office of Emergency Management would decide when people would be placed there.

Mr. Kagan, who also criticized the plan in a video he posted on Twitter, added that the struggle to house migrants was a nationwide problem and a shelter in a gym was not the answer.

The announcement comes one day after a Trump-era immigration policy called Title 42, which allowed for the rapid expulsion of migrants, ended Thursday night. The end of the pandemic-era policy is expected to lead to a rise in cross-border migration into the United States.

The city is in the middle of a “humanitarian crisis,” Fabien Levy, a spokesman for Mayor Eric Adams, said in a statement Friday evening, adding: “We are opening emergency shelters and respite centers daily, but we are out of space. We will continue to communicate with local elected officials as we open more emergency sites.”

New York City, which is the only major U.S. city with a “right-to-shelter” law, has struggled to house the influx of migrants who have been bused from states like Texas since last year. Mr. Adams has proposed, pivoted from and implemented many options for housing migrants over the past year, even considering placing people on a cruise ship docked in Staten Island.

Earlier this week, Mr. Adams used an executive order to temporarily suspend some of the rules related to its longstanding guarantee to shelter anyone who needs it, including those that require that families be placed in private rooms with bathrooms and kitchens and those that guide how quickly people must be placed in shelters.

“This is not a decision taken lightly,” Mr. Levy said in a statement Wednesday night. “And we will make every effort to get asylum seekers into shelter as quickly as possible, as we have done since Day 1.”

Increasingly frustrated in recent months, the mayor has criticized President Biden and pushed for federal emergency aid.

Earlier this month, Mr. Adams said the city was projecting that it would spend $4.3 billion over the next two fiscal years to cover the costs of the migrant influx and that roughly 37 percent of that was likely to be covered by the state and federal governments.

As the mayor desperately seeks places to house the migrants who are expected to arrive in the city, he also announced plans to begin busing migrants to other counties in the state, setting off a clash with other leaders. On Sunday, he told city leaders to send him a list of all facilities with enough space to accommodate large numbers of migrants.

In an hourslong call on Thursday with more than 100 officials from across the state, Mr. Adams heard complaints that he was not working effectively, adding to criticisms that he had not planned well for a problem he himself had been warning about for the past year.