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(CNN) —  

Hundreds of migrant children separated from their families at the southern border are in New York City. And Mayor Bill de Blasio says nobody told him they were there.

De Blasio said Wednesday that he just learned that 239 migrant children are in the care of Cayuga Centers in Harlem, which contracts with the federal government to help unaccompanied minors. The children include a 9-month-old, he said.

“How is it possible that none of us knew there were 239 kids right here in our own city?” the Democratic mayor said.

“How is the federal government holding back that information from the people of this city?”

Groups of children being dropped off at Manhattan foster care agency, which Mayor Bill de Blasio says houses more than 200 migrant children. It's unclear whether the children in the photo, who cover their faces, are among those separated from their parents.
PHOTO: Gabriella Bass
Groups of children being dropped off at Manhattan foster care agency, which Mayor Bill de Blasio says houses more than 200 migrant children. It's unclear whether the children in the photo, who cover their faces, are among those separated from their parents.

De Blasio said a total of 350 children have been in the care of the center since President Donald Trump’s administration implemented its “zero tolerance” policy calling for the prosecution of adults caught crossing the border illegally.

’Stop this right now’

At least 239 currently remain at the center, the mayor said. Cayuga Centers is not a residential facility, and runs programs for the children, some of whom are in foster care.

“And this is just one of the centers in New York City,” De Blasio said. It’s unclear how many separated children are in the city, and the mayor urged the federal government to “come clean” with that information so they can get the help they need.

Some of the children who come to the center daily for classes and social services have bed bugs, lice, chicken pox and other contagious diseases, he said. Some are too young to communicate and need significant mental health services.

De Blasio said the children should be with their parents.

“Stop this right now,” he said. “Stop this broken, inhumane policy right now.”

Night transfers

Mayor Bill de Blasio says some migrant children are taken to the Cayuga Centers facility in Harlem for daily classes. It's unclear whether the children in the photo were among those separated from their parents.
PHOTO: Gabriella Bass
Mayor Bill de Blasio says some migrant children are taken to the Cayuga Centers facility in Harlem for daily classes. It's unclear whether the children in the photo were among those separated from their parents.

A group of girls separated from their families after crossing the border was brought to the facility early Tuesday, according to a federal source briefed on the matter. CNN affiliate NY1 shot video of the 12:45 a.m. transfer at Cayuga Centers.

A woman escorting the girls told the affiliate they had not been separated from their parents, the station said. Cayuga Centers has not responded to CNN’s request for comment.

In recent weeks, federal authorities have asked Cayuga Centers to prepare for more arrivals, as the administration’s zero tolerance immigration policy began to take effect, according to the source.

On its website, the organization says it receives funding through the Office of Refugee Resettlement, which is under the US Department of Health and Human Services.

“These children are placed in Spanish-speaking foster homes as they await reunification with a family member or sponsor, or return to the country of origin,” Cayuga Centers says. The facility also provides long-term care for “unaccompanied youth that do not have sponsors” but are kept in the United States because their home countries are too dangerous, it says.

Cayuga has two other facilities in New York and others in Delaware and Florida.

De Blasio urged people not to direct their frustration at the children or facilities, saying the police department will be deployed to ensure they are protected.

The children who come to Cayuga live in foster homes, he said.

They were treated well there, he said, but they should be with their parents.

On Wednesday the President signed an executive order to prevent undocumented immigrant families from being separated at the US-Mexico border.

CNN’s Melanie Schuman and Rob Frehse contributed to this report.