A truck slammed into railings near the White House on Monday night in what may have been an intentional act, officials from the Secret Service said.
One man has been detained after the U-haul vehicle rammed into barriers on the north side of Lafayette Square, which is about a block away from the White House, shortly before 10pm.
“Preliminary investigation reveals the driver may have intentionally struck the security barriers at Lafayette Square,” Anthony Guglielmi, chief of communications for the Secret Service, said on Twitter.
Images and videos showed police recovering a Nazi flag from inside the truck at the scene in the aftermath of the crash.
Officers retrieved the red flag with a large swastika and other plastic evidence bags that had been laid out on the sidewalk after the crash and placed them back in the rear of the rented box truck, a Reuters photographer said.
US Park Police will file charges with investigative support from the Secret Service, Mr Guglielmi said.
There are no immediate reports of injuries or ongoing danger at the spot of crash.
A previous tweet from Mr Guglielmi said no one from the White House or the Secret Service was injured in the incident.
A video posted by a witness to the crash, Chris Zaboji, showed the truck driving into the barricades and, after crashing once, driving into them a second time.
The 25-year-old Zaboji, an airline pilot living in Washington, said he was walking home after jogging on the national mall when he heard a loud crash. The initial ramming made him take out his phone and start recording.
“I looked back and saw that the U-Haul van had rammed into the barricade. I backed away behind a guy on a golf cart and took the video on my phone. After I saw it rammed again I didn’t want to be anywhere near the truck and left,” he said.
Officials at the White House did not specify the exact location of president Joe Biden at the time. Just hours earlier on Monday evening, Mr Biden held a meeting with the speaker of the House of Representatives, Kevin McCarthy, at the White House.
The Washington DC fire department was informed of the incident at around 9.40pm (2.40am BST) and alerted of a “suspicious package investigation”, its spokesperson said.
Firefighters rushed to the spot alongside a major law enforcement and public safety response, before investigators determined the contents of the mostly empty truck were harmless.
The Secret Service also evacuated the nearby Hay Adams hotel by request, reported the Washington Post, citing a hotel official.
Some roads and pedestrian walkways around the park were closed, the Secret Service said.