WASHINGTON — The Secret Service said Tuesday it is investigating how an intruder was able to break into the home of White House national security adviser Jake Sullivan in the middle of the night a few weeks ago.

A spokesman said the agency is investigating «a security incident that took place at a protected site.»

«While the protégé was uninjured, we are taking this matter seriously and have opened a comprehensive mission assurance investigation to review all facets of what occurred,» spokesman Anthony Guglielmi said in a statement.

«Any deviation from our security protocols is unacceptable and if discovered, staff will be held accountable. Modifications have also been made to the security posture to ensure additional layers of security are in place while we conduct this comprehensive review,» he added.

Guglielmi did not say what happened to the intruder or if there was an interaction with Sullivan. The White House declined to comment.

The Washington Post, which first rexported the intrusion, citing three government officials who said the incident occurred around 3 am ET one night in late April and that Secret Service agents guarding Sullivan’s Washington home failed to detect the intruder.

Sullivan, 46, has been President Joe Biden’s national security adviser since the start of his presidency, and was Biden’s national security adviser from 2013 to 2014 when he was vice president. Sullivan held other positions in the Obama administration and was also a senior foreign policy adviser to former Secretary of State Hillary Clinton during her 2016 presidential campaign.

Elected officials and other public figures have faced increased threats in recent years.

On Monday, a 49-year-old Virginia man was charged with entering the D-Va. district office of Rep. Gerry Connolly with a metal baseball bat and attacking two of his staff.

In October, a man attacked Paul Pelosi, the husband of then-Speaker of the House Nancy Pelosi, D-Calif., with a hammer at their home in San Francisco. The accused man allegedly said that he was looking for the speaker at the time. He has pleaded not guilty to state and federal charges.