A US government investigation uncovered the potential use of sophisticated cell phone surveillance devices near the White House and other "sensitive facilities" in Washington last year.

It's not clear who may have operated the devices, known as IMSI catchers or Stingray devices, but it's possible they belonged to a foreign adversary.

Sen. Ron Wyden is calling on the Federal Communications Commission to do more to protect the communications of American citizens.

A US government investigation uncovered the potential use of sophisticated cell phone surveillance devices near the White House and other "sensitive facilities" in Washington last year, according to a letter recently sent to Democratic Sen. Ron Wyden by the Department of Homeland Security (DHS).

It's not clear who may have operated the devices, known as IMSI catchers or Stingray devices, but it's possible they belonged to a foreign adversary. IMSI catchers work by mimicking phone towers, which fools cell phones and allows the devices to intercept calls, texts, and data streams, according to The Washington Post.

The May 22 DHS letter to Wyden stated that a study conducted from January to November of 2017 found "anomalous activity that appeared consistent with IMSI catcher technology within [Washington DC], including locations in proximity to potentially sensitive facilities like the White House."

DHS had previously communicated to Wyden that there were signs IMSI trackers were being used in the Washington, DC area, but this is the first time federal officials have acknowledged the potential use of these devices near the White House.

Wyden expressed concerns about the implications of this discovery in a statement on Thursday.

"This admission from DHS bolsters my concern about stingrays and other spying devices being used to spy on Americans' phones," Wyden said.

"Given the reports of rogue spying devices being identified near the White House and other government facilities, I fear that foreign intelligence services could target the president and other senior officials," the senator added.

President Donald Trump has reportedly been using a private cell phone for calls with certain advisers and lawmakers despite warnings that this could make his communications more susceptible to hacking. Wyden addressed this in a statement on Friday, criticizing Trump for his "cavalier attitude" toward national security.

"The news of a possible foreign stingray near the White House is of particular concern given reports that the President isn't even using a secure phone to protect his calls. The cavalier attitude toward our national security appears to be coming from the top down," Wyden said.

The letter sent to Wyden also said federal officials had encountered reports that "nefarious actors may have exploited" a global cellular network messaging system called SS7 to "target the communications of American citizens."

Along these lines, Wyden has been calling on the Federal Communications Commission to do more to protect the communications of Americans, and on Thursday tweeted, "The FCC can & should conduct an independent assessment of the security of US phone networks, identity which networks are lagging behind, & then force those companies to up their security."