The U.S. ambassador to Belgium, Bill White, booked a public park in Brussels for an invitation-only party to celebrate 250 years of American independence last weekend. There were lobster rolls, country music and fireworks.

Evidently, there was also damage.

The fireworks display left black marks on a building in the Cinquantenaire Park, Mr. White confirmed by phone on Friday. He said the fireworks company hired for the event would handle the repairs and said that a storm the night before the event may have washed protective coating from the structure.

“There are some black soot marks on the top of the monument where the fireworks went off,” Mr. White said, explaining that he had been in touch with the mayor of Brussels, Philippe Close, about the issue. The building in question houses the Royal Museums of Art and History, according to the local building authority.

Mr. Close did not immediately respond to a request for comment.

Possible damage to the museum in the Cinquantenaire Park was reported earlier this week by two Belgian news outlets, De Standaard and Het Nieuwsblad. Shortly after the news broke, Mr. White posted on social media that he was “in immediate contact with the Belgian company that was hired to coordinate all event logistics.”

“Cinquantenaire has never looked any cleaner than it was the day after we cleaned up after our event,” he added.

The office of Vanessa Matz, who oversees the Belgian Buildings Agency, said in a statement on Friday afternoon that the agency was conducting an analysis of the damage to the roofs and cornices, adding that it could also have been linked to the storms.

Many of the Cinquantenaire Park’s structures were constructed in the late 1800s and early 1900s. The event celebrating 250 years of U.S. independence was framed against the park’s triumphal arch, which is topped with the statue of a bronze chariot and is a symbol of Brussels.

The celebration was attended by thousands of people. It included performances by the country music singer Alexis Wilkins, who is dating Kash Patel, the F.B.I. director; and Zac Brown Band, a country group. Mark Rutte, the Secretary General of NATO, and Bart De Wever, Belgium’s prime minister, were among the high-ranking European officials who attended.

The event also drew criticism. Protesters shouted loudly outside of the park as the evening kicked off. Media in Brussels alternately described the party as the “hottest ticket” and “divisive.”

Like similar parties across the continent, the Brussels bash came against the backdrop of a diplomatic tug of war. Over the past 18 months, Mr. Trump has increased tariffs on Europe, threatened to take over Greenland and repeatedly questioned the U.S. commitment to NATO, disturbing the close relationship that has defined the global order since the end of the Second World War.

As the trans-Atlantic relationship deteriorates, Brussels, which is home to NATO and to the institutions of the European Union, has felt the consequences. Some officials at the event nodded to that tension.

“Like in any marriage, we have disagreements,” Roberta Metsola, the president of the European Parliament, said at the party.

Mr. White, who was appointed by Mr. Trump, is the former chief executive of the Intrepid Museum in New York and has cut a colorful figure in Belgium. He threw an ornate party earlier this year to screen “Melania,” a documentary about the first lady, and has drawn rebuke for being unusually outspoken on domestic issues in his host country.

At the U.S. independence event last Sunday, Mr. White used his remarks to unveil a ring encrusted with diamonds from Antwerp as a gift from the city’s diamond sector to President Trump.

He also called out the American pop singer Katy Perry, whom he had talked about as a possible performer, for having missed the bash.

“So we were going to have Katy Perry. Who cares?” he said at the event.

Mr. White said on Friday that he would be cheering for the U.S. team when they play Belgium in a World Cup soccer match on Monday.