U.S. emergency services on Sunday identified a white powder found inside the White House as cocaine, a source confirmed Tuesday.

The source said the powder was found in the West Wing, but gave no further details.

The West Wing is attached to the executive mansion where President Joe Biden lives. It houses the Oval Office, the cabinet room and press area, and offices and workspace for the president's staff.

Hundreds of people work in or come through the West Wing regularly.

The Secret Service said Tuesday that an "unknown item" had been found in a workspace within the West Wing on Sunday, leading to the temporary closing of the White House complex.

"On Sunday evening, the White House complex went into a precautionary closure as officers from the Secret Service Uniformed Division investigated an unknown item found inside a work area," a Secret Service spokesperson said in an emailed statement.

A second source familiar with the matter said the substance was found during a routine Secret Service sweep of the area.

It was later identified as cocaine.

"The DC Fire Department was called to evaluate and quickly determined the item to be non-hazardous," the Secret Service spokesperson said, adding there was "an investigation into the cause and manner" of how the substance entered the White House.

Biden was not in the White House on Sunday. He and his family returned from a weekend at the presidential retreat Camp David on Tuesday morning.

The Washington Post first reported the discovery.