Someone threw what appeared to be a smoke bomb over the White House fence Tuesday night, according to the Secret Service.
The incident took place during an Occupy DC rally outside the White House.
About 1,000 protesters participated in the rally.
No one was arrested, according to Secret Service spokesman George Ogilvie.
While the situation was handled, people inside the White House were prevented from leaving on the Pennsylvania Avenue side.
The president and first lady were not home at the time. They were out having dinner for Michelle Obama's 48th birthday.
Thousands of protesters were in town Tuesday for a loosely-organized event called "Occupy Congress." Demonstrators massed outside the Capitol to welcome lawmakers back from their winter recess.