Entrances to the White House (search) from Pennsylvania Avenue, a historic Washington thoroughfare, were briefly closed on Wednesday and workers already inside were told to remain in the building.

The shutdown lasted about 20 minutes. U.S. Secret Service officers on the scene said the incident was prompted by discovery of a suspicious package inside the fence around 9 a.m.

Secret Service spokesman Eric Zahren told The Associated Press there was nothing to it. Zahren said "standard procedures were taken" to check out the package.

Zahren said it's unclear what was in the package. It is unknown if President Bush was at the White House at the time.