A white powder discovered in a lobby area of the White House’s West Wing that prompted a brief evacuation Sunday evening tested positive for cocaine in a laboratory analysis, three people familiar with the matter said Wednesday.

Officials who found the powder in a small plastic envelope in the heavily trafficked part of the White House initially suspected illegal drugs, but they ran tests to ensure that the powder was not a more dangerous substance. Investigators have not yet identified who brought the cocaine into the White House, according to the three people, who were not authorized to publicly discuss the inquiry and spoke on condition of anonymity.

President Joe Biden was at Camp David with members of his family for the holiday weekend when the powder was discovered and the complex was briefly evacuated as a precaution. It’s routine for emergency teams to quickly test a suspicious substance on the scene to determine whether it’s hazardous and also to follow up with a more sensitive lab tests later.

The U.S. Secret Service, which is responsible for securing the White House, was taking the lead on the investigation, consulting visitor logs and security footage.

The lobby is where many official visitors and staffers enter. It is also open to staff-led tours of the West Wing, which are scheduled for nonworking hours on the weekends and evenings.

The Secret Service said in a statement Tuesday the White House was closed as a precaution as emergency crews investigated, and that the District of Columbia Fire Department was called in to evaluate and determine that the substance was not hazardous.

“The item was sent for further evaluation and an investigation into the cause and manner of how it entered the White House is pending,” the Secret Service said.