The white powder discovered at the White House that has tested positive for cocaine was found near a spot where visitors getting private tours leave their cellphones, according to new reporting from The Washington Post. The paper—citing three individuals close to the investigation—said officials found the cocaine near a set of boxes where tour guests stash their phones before entering the West Wing. White House staffers usually give those tours at night or on the weekends. Because of its location, the cocaine’s owner will be “difficult” to find, an anonymous official familiar with the investigation told Politico. “Even if there were surveillance cameras, unless you were waving it around, it may not have been caught,” the official added. “It’s a bit of a thoroughfare. People walk by there all the time.” The white powdery substance sparked a brief evacuation of the building on Sunday, and authorities are now investigating where it came from. President Biden, who spent the weekend at Camp David, wasn’t in the White House at the time of the discovery.