The US Secret Service on Wednesday confirmed that a powdery substance found inside the White House over the weekend is cocaine.

The cocaine was discovered in an area of the West Wing lobby where individuals can store their phones, according to Anthony Guglielmi, a spokesperson for the Secret Service. The lobby is “a heavily traveled area” regularly accessed by both visitors and staff, White House Press Secretary Karine Jean-Pierre said Wednesday.

“The president thinks this is incredibly important to get to the bottom of,” she added.

The Secret Service, which protects the president and other high-level US officials, conducted its own analysis after an initial field test by the D.C. fire department indicated the substance was cocaine. The White House complex was evacuated Sunday after officials found the powder.

The D.C. fire department’s hazmat team responded and deemed the substance not to pose a threat to the complex.

The White House declined to say whether it would want to see a criminal prosecution if a specific individual were found to be responsible for bringing the cocaine into the complex, or whether staffers would face new drug tests or screening after the incident. Biden was briefed by his staff about the progress of the investigation, Jean-Pierre said.

White House grounds are highly secured by the Secret Service, with assistance from local law enforcement. Staff and visitors are regularly screened at a security checkpoint and typically must submit to a background check.