Lab testing for the substance found at the White House on Sunday has come back positive for cocaine, a spokesman for the Secret Service told CNN. Prior field testing showed a positive result for cocaine, but the substance was sent for further evaluation and testing, the Secret Service had previously said. The substance was found near the ground floor entrance to the West Wing, a person familiar with the matter said. The location is where staff-led tours of the White House pass through on their way into the building. The substance was found near where guests are asked to leave their cell phones before proceeding into the West Wing. Those tours typically only occur on weekends. Sources had previously described the substance as a white powder found in a small, zipped bag. It was found by Secret Service personnel conducting routine rounds of the building. White House press secretary Karine Jean-Pierre said Wednesday the White House is confident the Secret Service will “get to the bottom” of the incident. She confirmed the cocaine was discovered in a “heavily traveled area” of the West Wing that visitors, as well as staff, pass through. President Joe Biden was briefed on the situation and “everything we know so far,” Jean-Pierre said, noting the Secret Service was conducting an investigation. “We have confidence that they will get to the bottom of this,” she said. She said tours of the building recently occurred on Friday, Saturday and Sunday. But asked whether it was a working theory that a tour guest was the culprit, she demurred. “It is where visitors to the West Wing come through,” she said. “I’m not going to speculate on who it was.” A federal law enforcement official told CNN that additional tests being done on the bag include DNA and fingerprint analysis. The Secret Service, the official said, is doing “everything possible” to try and identify who brought what the official described as a “dime-sized bag” into the West Wing. The official noted that identifying the culprit may be difficult because of the size of the bag and the number of people who would have had access to the area. The Secret Service is going through visitor logs, surveillance video and relying on the analysis of the bag to try to advance their investigation, the official explained. The baggie, the official said, was not found on the ground, but in a cubby where visitors entering the West Wing are asked to leave their phones. These cubbies can also be used by staff who cannot bring their phones into a SCIF, or sensitive compartmented information facility, where classified materials are handled. The discovery of the substance Sunday evening triggered a brief evacuation as part of what the Secret Service described as “precautionary closures.” Biden was at Camp David over the weekend and returned to the White House Tuesday morning. This story has been updated with additional reporting.