Immigration and Customs Enforcement officials are planning a monthlong series of raids, according to a Reuters report.

ICE notified field offices across the country that the 30-day "surge" will target mothers and children from Central America who were previously told to leave the U.S., according to a document seen by Reuters. 

While the locations of the raids are unknown, New York immigrant advocates are concerned about the implications for the city.

"If immigration comes looking for very specific individuals, they will ask for identification and papers for the rest of the people in the house," says Lymari Casa, of the Casa Law Firm. "This could lead to more arrests than the actual people they're looking for."

In a Facebook post, Mayor Bill de Blasio denounced the raids. "Many of these families have fled violence in their home countries and seek safety here, in the city of immigrants. The City of New York is in no way involved in these reported immigration enforcement actions."

The raids, which are expected to start sometime this month and continue through June, come after a deportation operation in January that targeted immigrants in Texas, Georgia and North Carolina. The raids resulted in the deportation of more than 100 people, mostly women and children, according to the Reuters report.

Casa advises people who have unresolved deportation issues to consult an immigration professional because she says there will be no warning before agents knock on doors.