The US Secret Service and US Capitol Police responded to two security incidents on Monday - both of which proved to be false alarms - as Washington, DC, hosted a summit gathering nearly 50 African leaders.
The US Secret Service cleared Pennsylvania Avenue in front of the White House and closed one of its gates for more than an hour after a bomb-sniffing dog alerted them to a car in a nearby garage.
A Secret Service spokesman later said the all-clear was given at 9:20am EDT (1320 GMT), indicating there was no danger posed.
Pedestrians had earlier been told by the Secret Service and US Park Police that the area was closed. White House staff and journalists were not allowed through the northwest gate but some personnel were allowed to use the east gate.
Around the same time, the US Capitol police closed streets at one of the US Senate office buildings because of a suspicious package. But at 10:00am (1400 GMT), they announced the all-clear and said the roads had been reopened.
Security is particularly high in downtown Washington, with many streets shut, as the US capital hosts a summit of African leaders Monday through Wednesday intended to showcase US interest in the fast-growing region.
The closure of Pennsylvania Avenue, which is open only to pedestrian traffic and official vehicles on the White House block, came after a bomb-sniffing dog alerted officers to a car parked in the garage of the nearby New Executive Office Building, a Secret Service spokesman said.
Washington city police had been examining the car.