A swastika drawn on a window shade in purple ink was found inside the US embassy in Bulgaria last month, Axios reported on Sunday.
News of the discovery circulated in Washington on Friday after the embassy in Sofia sent back a diplomatic cable describing the incident.
The image was first identified on January 28, a day after International Holocaust Remembrance Day, according to Axios.
The swastika was found in a secure part of the embassy, indicating whoever drew it had access inside an American diplomatic outpost, according to sources with knowledge of the cable.
"The department takes this matter extremely seriously," said State Department spokesperson Ned Price, adding, "We unequivocally condemn any instances of hate or bias in the workplace, which this appears to be."
"This is a repugnant symbol that stands for everything we as a department are standing against," he continued. "We are committed to doing everything possible to ensure the State Department, including our posts overseas, remain a welcoming, inclusive and bias-free workplace."
This past July, a swastika was found carved into an elevator at the State Department building in Washington, DC.
The incident was condemned by President Joe Biden, who said, “Let me be clear: Anti-Semitism has no place in the State Department, in my Administration, or anywhere in the world. It’s up to all of us to give hate no safe harbor and stand up to bigotry wherever we find it.”
US Secretary of State Antony Blinken, who is Jewish, condemned the incident in an email to State Department employees.
"The hateful graffiti has been removed and this incident will be investigated," Blinken wrote, calling anti-Semitism an "abhorrent" hatred that "has no place in the United States, at the State Department or anywhere else."
"To our Jewish colleagues: please know how grateful we are for your service and how proud we are to be your colleagues," he added.