A New York City Council employee was detained during a “routine” immigration appointment on Long Island on Monday, according to city officials, who called the incident an “egregious government overreach.”

Mayor Zohran Mamdani said he is “outraged” by the worker’s arrest.

“This is an assault on our democracy, on our city, and our values,” he said in a statement on X. “I am calling for his immediate release and will continue to monitor the situation.”

The employee was detained by federal immigration officials during an appointment in Bethpage in Nassau County earlier Monday, according to NYC Council Speaker Julie Menin.

The city council learned of his detainment Monday afternoon, when the employee used his one phone call to contact the council’s human resources department for help and said he had been detained, according to Menin.

“DHS confirmed that this employee had gone in for a routine court appointment and was nevertheless detained. They provided no other basis for his detainment,” Menin said during a press briefing on Monday. “On the contrary, he was a city council employee who is doing everything right. He went to the court when he was asked.”

Menin said the city council is demanding the return of the employee, whom she did not identify, citing privacy concerns. He is a “central staff member working as a data analyst for approximately a year,” she said.

The speaker said the employee has legal authorization to remain in the country until October.

Democratic New York Congressman Dan Goldman said the employee is of Venezuelan descent and is a “law-abiding immigrant with work authorization.”

“I want to be very clear: There is no indication that there’s anything about this individual other than his immigration status that caused him to be arrested,” he said during Monday’s press briefing.

The employee has been transferred to a detention center in Manhattan, according to Menin. She said the city council has been unable to reach his family members.

Goldman said his office has reached out to U.S. Immigration and Customs Enforcement.

“We will continue to fight this,” he said. “We will continue to push for not only this person’s release, which is so obviously necessary, but for this immigration dragnet to stop.”

New York Attorney General Letitia James also called for the staffer’s immediate release, saying in a statement on X, “We will not stand for attacks on our city, its public servants, and its residents.”