Intensifying its enforcement in so-called sanctuary cities across the country, Immigration and Customs Enforcement has begun 24-hour-a-day surveillance operations around the homes and workplaces of undocumented immigrants. The agency plans to deploy hundreds of additional officers in unmarked cars in the coming weeks to increase arrests in cities where local law enforcement agencies do not cooperate with federal immigration enforcement.

ICE leadership has requested at least 500 special agents who normally conduct long-term investigations into dangerous criminals and traffickers to join the enhanced arrest campaign rolling out in sanctuary cities, according to an internal email reviewed by The New York Times.

The request follows an earlier decision, made public last month, to deploy elite tactical BORTAC agents — immigration SWAT teams that are normally assigned to risky border smuggling, rescue and intelligence operations — to help arrest and deport immigrants in sanctuary cities.

The expanded surveillance operations and added manpower are the latest intensification in a conflict between the Trump administration and cities that refuse to help with deportations, including Boston, New York, Detroit, Chicago, San Francisco, Los Angeles, Atlanta, New Orleans and Newark. The effort began last month and will run through Dec. 31, according to the internal email, which says the initiative is called Operation Palladium.