A suspected smoke bomb tossed over the fence of the White House caused a temporary lockdown of the compound late on Tuesday, as hundreds of Occupy protesters had gathered outside the gates.

People inside the White House were initially prevented from leaving but were later released through a side exit.

No arrests have been made over the incident, Secret Service spokesman George Ogilvie has said. A majority of the protesters had left the area earlier.

The Obamas were at dinner celebrating Michelle Obama's birthday when the incident occured, but they have sunsequently returned to the White House without difficulty, Fox News reports.

Earlier, protesters from the Occupy movement gathered at the congressional buildings to protest against the influence of large corporations on lawmakers.

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