Authorities temporarily placed the White House on lockdown after someone threw a metal object over the fence around the presidential mansion, officials said.
Reporters working at the White House said a woman had been arrested.
"An individual threw a metal object over the north fence line at the White House," the Secret Service said in a statement after the approximately three-hour lockdown ended.
"Secret Service uniformed division officers immediately apprehended the individual without incident."
Officials said they conducted "protective sweeps" of the object but determined it was not a threat.
"The White House has returned to normal operations," the Secret Service said.
President Barack Obama had been attending a Memorial Day service at Arlington National Cemetery when the incident occurred.
