The warning came after the department discovered that an impostor posing as Rubio had attempted to reach out to at least three foreign ministers, a U.S. senator and a governor, according to the July 3 cable, which was first reported by The Washington Post.

The recipients of the scam messages, which were sent by text, Signal and voice mail, were not identified in the cable, a copy of which was shared with The Associated Press.

“The State Department is aware of this incident and is currently investigating the matter,” it said. “The department takes seriously its responsibility to safeguard its information and continuously takes steps to improve the department’s cybersecurity posture to prevent future incidents.”

It declined to comment further due to “security reasons” and the ongoing investigation.

One of the officials said the hoaxes had been unsuccessful and “not very sophisticated.” Nonetheless, the second official said the department deemed it “prudent” to advise all employees and foreign governments, particularly as efforts by foreign actors to compromise information security increase.

The officials were not authorized to discuss the matter publicly and spoke on condition of anonymity.

“There is no direct cyber threat to the department from this campaign, but information shared with a third party could be exposed if targeted individuals are compromised,” the cable said.

The FBI warned in a public service announcement this past spring of a “malicious text and voice messaging campaign” in which unidentified “malicious actors” have been impersonating senior U.S. government officials.

The scheme, according to the FBI, has relied on text messages and AI-generated voice messages that purport to come from a senior U.S. official and that aim to dupe other government officials as well as the victim’s associates and contacts.

It is the second high-level Trump administration official to face such AI-driven impersonation.

The government was investigating after elected officials, business executives and other prominent figures received messages from someone impersonating President Donald Trump’s chief of staff, Susie Wiles. Text messages and phone calls went out from someone who seemed to have gained access to the contacts in Wiles’ personal cellphone, The Wall Street Journal reported in May.

Some of those who received calls heard a voice that sounded like Wiles, which may have been generated by artificial intelligence, according to the newspaper. The messages and calls were not coming from Wiles’ number, the report said.

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AP writer Eric Tucker contributed to this report.