U.S. Customs and Border Patrol agents have been seen at South Florida Greyhound bus stations asking riders for proof of legal status, the Miami Herald is reporting.

It is part of an effort to apprehend undocumented immigrants in South Florida. The agents have been spotted at Greyhound bus stations in Miami-Dade and Broward counties. They are reportedly asking riders on buses or those in the process of getting on board for documentation of their status.

"U.S. Border Patrol has been performing enforcement actions away from the immediate border in direct support of border enforcement efforts and as a means of preventing trafficking, smuggling and other criminal organizations from exploiting our public and private transportation infrastructure to travel to the interior of the United States," the U.S. Border Patrol said in a statement to the Herald.

"Agents in Florida enforce immigration law while working closely with local, state and federal law enforcement partners to keep communities safe while securing the coastal borders."

Those who can't fly because of their illegal status often take trains or Greyhound buses, immigration attorney Tammy Fox-Isicoff told the Herald.

"This is known, especially to ICE and CBP," she said.

Meanwhile, Greyhound told the newspaper that the "CBP searches have negatively impacted both our customers and our operations."

The American Civil Liberties Union has called on Greyhound to stop allowing immigration agents from boarding its buses, according to Newsweek.

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