A bomb technician works with an explosives ordinance disposal robot to help recover an unknown item that was thrown over the fence on the north side of the White House in Washington. Picture: Pablo Martinez Monsivais

Washington - Two individuals threw items over the White House fence on Thursday, triggering the second lockdown at the president's residence this week.

President Barack Obama was travelling in California and was not at the White House when the items were thrown.

A spokesman for the Secret Service said the two people had been taken into custody and the suspicious items were being examined.

A car that trailed a motorcade carrying Obama's children on to Pennsylvania Avenue in front of the White House led to a security lockdown on Tuesday that lasted more than an hour. - Reuters