A 23-year-old woman armed with a handgun was arrested outside the White House late Thursday, US Secret Service officials said.
In a statement released Friday, the Secret Service identified the woman as April Lenhart of Mount Morris, Michigan.
"Lenhart was participating in a demonstration along the north fence line of the White House complex when Secret Service personnel monitoring the demonstration observed a holstered handgun on Lenhart's front hip," said the agency, which is tasked with protecting the president, visiting dignitaries and top US officials.
Lenhart was arrested and charged with possession of an unregistered firearm, possession of unregistered ammunition and carrying a pistol without a license, the Secret Service said.
Her arrest came just one day after Secret Service officers arrested a 41-year-old man at the White House who had a rifle and ammunition in a car parked nearby.
US media said the man on Wednesday approached a Secret Service officer at 15th Street entrance of the White House, saying someone told him to go to the White House.
A search of his car, parked about a half-mile (0.8 kilometers) from the White House, yielded a hunting rifle and ammunition, news reports said.
The Secret Service has beefed up its operations after a string of security lapses, including one involving an armed intruder who scaled the White House fence and  managed to get well within the presidential mansion.
Secret Service director Julia Pierson was forced to resign last month in the aftermath of the breaches.