For the second time in three days, the White House was on lockdown Thursday because of a security breach. The Secret Service said that two people threw something over the fence surrounding the White House complex - one person from the south side and one from the north. The two people were being detained and questioned. Secret Service officers were ordering people in the West Wing to stay inside. The incident follows an hour-long lockdown Tuesday after a vehicle followed a motorcade bringing President Barack Obama's daughters home through the gates. The driver was charged with unlawful entry, a misdemeanor.