Police on Wednesday sealed off the front gates of the White House and cleared Lafayette Park across from the executive mansion as a bomb squad converged on the area to investigate the object.
  
George Bush, the US president, was not at the White House at the time and the grounds were not evacuated.
   
The package, thrown over the fence on the White House's north side, was found to be harmless, said Tom Mazur, spokesman for the Secret Service.
   
"That package has been rendered safe," he said.
   
Authorities sent a small remote-controlled robot onto the White House grounds to check out what appeared to be a small white package. The robot picked up the object and brought it back to the driveway.
   
Reporters and camera crews were ordered inside the White House press room and could only monitor the situation by peering through the windows.
   
Police later approached a man in Lafayette Park and put him in a car with handcuffs.
  
"An individual threw the suspicious package over the north fence line. He is in custody," Mazur said.
   
Mazur said a similar incident had occurred before involving the same man. Even though past incidents had not involved explosives, officials proceeded with bomb-investigating procedures as a precaution.