The White House was placed on temporary lockdown Monday afternoon after a woman threw an object over the north fence along Pennsylvania Avenue.
Around 12:15 p.m., the woman, who was not immediately identified, threw something over the north fence of the White House, prompting the lockdown, the Secret Service said in a statement.
Secret Service officers "immediately apprehended the individual without incident," according to the statement.
The lockdown was lifted around 3 p.m.
Reporters were not allowed to venture out of the White House press room during the lockdown.
Fire trucks and a hazardous materials response unit were called to the scene. It is common for officers to sweep the grounds after such incidents to ensure nothing dangerous was thrown over the fence.
The lockdown ensued shortly after President Barack Obama returned from delivering a Memorial Day speech at Arlington National Cemetery.
The White House has since resumed normal operations.
The Associated Press contributed to this report.