Updated

Maggiano's, a popular Italian restaurant chain, has issued a public apology, saying it unintentionally hosted a white nationalist group at one of its Washington, D.C.-area locations and the diners performed a Nazi salute while eating there.

The restaurant said it didn’t realize it was hosting a banquet Friday for a group called the National Policy Institute, whose official website says it advocates for the heritage and identity of those of European descent in the US.

Protesters soon took notice and forced the restaurant to abruptly close. But the restaurant said that the dinner was hosted accidentally and that the group made reservations at the last minute using a different name. The group was gathered in Washington for a conference and celebrated Republican Donald Trump’s election.

On Monday, Maggiano's Chevy Chase posted an apology to its official Facebook page:

“The protesters were upset because of a banquet we were hosting for a group called the National Policy Institute (NPI),” the statement read.

“This was a last minute booking made Friday afternoon, and the reservation was made under a different name, therefore we were not aware that NPI was dining with us or what the group represents.

“After the event, an attendee sent a tweet in which she made a ‘Sieg Heil salute’ in support of Hitler and white supremacy. This expression of support of Hitler is extremely offensive to us, as our restaurant is home to Teammates and Guests of every race, religion and cultural background.”

“We want to sincerely apologize to the community of Friendship Heights for inadvertently hosting this meeting, which resulted in hateful sentiment.”

CBS reported that fights between NPI supports and protesters, meantime, lead to multiple arrests and injuries.

The Associated Press contributed to this report.