A man is in custody after a car drove up to a White House checkpoint on Saturday night, the US Secret Service has said.
Security at the White House was immediately upgraded. CNN reported the driver claimed to have a bomb.
The vehicle has been declared suspicious and nearby streets have been closed off.
US President Donald Trump was at his Mar-a-Lago resort in Florida at the time of the incident.
The Secret Service, which handles White House security, said the driver had approached a “checkpoint located at 15th Street and E Street NW” at around 23:05 local time (03:05 GMT).
The man was then detained by officers.
- White House intruder jumped three fences
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The episode was the second scare to hit the White House on Saturday, after a person earlier jumped over a bike rack in a buffer zone in front of the residence.
White House spokesman Sean Spicer tweeted that the unnamed person had been unable to make it into the grounds, and praised the “great response” by the Secret Service.
The agency has been heavily criticised this week in the wake of a fence-jumping incident on 10 March, when an intruder was discovered just steps from the main building.
Jonathan Tran, 26, was in the White House grounds for more than 16 minutes before he was detained.
The Secret Service said it had taken immediate steps to avoid further security lapses as a result of the breach.