The U.S. Marshals Service is harvesting large amounts of data from Americans’ cellphones through devices mounted on airplanes in an effort to locate fugitives, according to two individuals familiar with the activity.

The program operates Cessna aircraft from at least five metro-area airports and collects data from law-abiding Americans as well as criminal suspects, according to the Wall Street Journal, which first reported the story Thursday.

According to the Journal, the planes are equipped with two-foot-square devices — sometimes called “dirtboxes” — that mimic cell towers and trick cellphones into reporting their unique registration information and general location.

The Marshals Service, which protects the federal judiciary and apprehends federal fugitives, is a component of the Justice Department.

Officials at the Justice Department would neither confirm nor deny the existence of the program.

“Discussion of sensitive law enforcement equipment and techniques would allow criminal defendants, criminal enterprises or foreign powers to determine our capabilities and limitations in this area,” said one department official who provided a statement on the condition of anonymity. “In deploying any such equipment or tactics our federal law enforcement agencies comply with federal law, including by seeking court approval.”

News of the program comes after disclosures by former National Security Agency contractor Edward Snowden of broad government surveillance activities. One NSA program revealed last year collects data on phone calls — though not the content of calls — of millions of Americans inside the United States in an effort to track terrorists. Congress is weighing legislation to end the NSA’s collection of phone “metadata,” and the federal courts are hearing challenges to that program’s constitutionality.

In some respects, the technology used by the Marshals Service is similar to that used by the FBI, whose agents sometimes deploy StingRay devices in vehicles to collect the serial numbers of individual cellphones and locate them. Privacy groups and some judges have raised concerns that the StingRay technology is so invasive — in some cases penetrating the walls of homes — that its use should require a warrant.

Some judges say that federal agents are not providing enough evidence to justify the use of the StingRay, which sweeps up data not only from a suspect’s phone but also from those of bystanders.

According to the Journal, the technology used by the marshals is more sophisticated than the StingRay. Because the devices are deployed in the air, they can gather more data than a device in a car on the ground. If a suspect’s phone is identified, the technology can pinpoint its location within about three meters, or to a specific room in a building, the Journal said.

The Marshals Service, the nation’s oldest federal law enforcement agency, also operates the witness security program and seizes assets acquired by criminals through illegal activities.