A lockdown at the White House has been lifted and one person is in custody after reports of "suspicious activity" along the north fence of the 18-acre complex.

The US Secret Service tweeted: "Subject is in custody."

Update: subject is in custody, Lafayette Park & North Fence line along Penn. Ave. remain closed.

— U.S. Secret Service (@SecretService) November 3, 2017

Pennsylvania Avenue and Lafayette Park were closed to pedestrians near the White House.

Reporters and staff were instructed not to leave while the investigation continued, but were later allowed to exit.

The incident came minutes after President Donald Trump departed the White House on Marine One to begin his trip to Asia.

Update: subject is in custody, Lafayette Park & North Fence line along Penn. Ave. remain closed.

— U.S. Secret Service (@SecretService) November 3, 2017