The White House was locked down and two people detained Thursday after they allegedly threw items over the presidential mansion's fence, the Secret Service said.

According to agency spokesman Ed Donovan, one individual threw an item over the White House's north fence, while another individual threw an item onto the South Lawn. Both were put into custody, and the Secret Service was working to clear the items.

President Obama was traveling in California at the time of the incident.

The arrests came two days after a man was arrested for following a motorcade carrying the Obamas' daughters as it entered the White House complex. 

55-year-old Mathew Evan Goldstein was arrested and charged with unlawful entry, according to the Secret Service. Goldstein, an IRS employee, told officials he had simply made a mistake, a federal official told The Washington Post.

“He was at a function downtown with colleagues and said he was just checked out mentally and confused,” the official said. “It seems to be bad luck on his part.”