British Prime Minister Andy Burnham exchanged messages with someone impersonating one of US President Donald Trump’s closest advisers, four officials have told Politico.

Burnham communicated with a person posing as White House Chief of Staff Susie Wiles before growing suspicious that the individual was not who they claimed to be, according to the same officials.

“We do not comment on national security matters,” Downing Street said.

A person briefed on the exchanges said “a few messages” were sent after Burnham took office, though they maintained the content “held no significance.”

The British embassy in Washington was concerned enough about the incident to raise it with the White House, according to two of the officials, who spoke on condition of anonymity given the sensitivity of the matter, which touches on national security.

Within the British government, there were fears that Wiles’s phone may have been compromised again. The White House declined to comment on the incident.

Similar breach reported at the White House last year

Last year, the White House and the FBI opened an investigation after senators, governors and US business executives received text messages and phone calls from someone claiming to be Trump’s chief of staff.

The Wall Street Journal reported at the time that Wiles had told associates that the contacts stored on her phone had been hacked.