McALLEN, Texas (AP) — The Trump administration has launched a review of organizations that provide temporary housing and other aid to migrants, suggesting they may have violated a law used to prosecute smugglers.

The Department of Homeland Security has “significant concerns” that federal grants used to address a surge of migration under former President Joe Biden were used for illegal activities, wrote Cameron Hamilton, acting administrator of the Federal Emergency Management Agency.

His letter, dated Tuesday and obtained by The Associated Press, asks recipients of grants from FEMA’s Shelter and Services Program to provide names and contact information for migrants served and “a detailed and descriptive list of specific services provided” within 30 days. The letter says funding will be withheld during the review.

While it doesn’t explicitly threaten criminal prosecution, it raises concerns that recipients may have violated U.S. Criminal Code Section 1324, a felony offense against bringing people across the border illegally or transporting them within the United States. It also says executive officers must sign sworn statements that they have no knowledge or suspicions of anyone in their organizations violating the smuggling law.

FEMA did not immediately respond to a request for comment late Wednesday.

The demand appears to be a new salvo against organizations that provide food, housing and travel aid to people who cross the border. Migrants often arrive exhausted, low on money and unsure how to navigate on their own through bus stations and airports.

Texas Gov. Greg Abbott, a Republican who was at odds with the Biden administration over immigration and is closely aligned with the Trump White House, took a similar tack against migrant aid groups but was blocked in court.

FEMA’s Shelter and Services Program awarded $641 million to dozens of state and local governments and organizations across the country in the 2024 fiscal year to help them deal with large numbers of migrants who crossed the border from Mexico. They include the cities of New York, Philadelphia, Chicago and Denver, as well as the United Way of Miami, the San Antonio Food Bank and several branches of Catholic Charities.

It was unclear if any any governments received the letters, but the Trump administration has fiercely criticized states, counties and cities that limit cooperation with federal immigration authorities. Last month, it sued Chicago over laws that it said thwarted federal law enforcement.