12:30 PM PT -- Former Secret Service agent Bobby McDonald says the Secret Service doesn't have video footage of who left their cocaine in the White House because the area where it was found is lacking security cameras.
Bobby joined us on "TMZ Live" Thursday and explained why the area of the West Wing where the cocaine baggie was found isn't closely monitored with video surveillance ... though he thinks the Secret Service will use the incident to implement some changes.
He says the Secret Service narrowed down the list of possible suspects, based on who was in the area during the time frame, but without video or physical evidence to nail a culprit ... the case is now closed.
Whoever left their coke in the White House can smile ... they're not gonna get busted for it, because the Secret Service has no video evidence to nail a suspect.
The Secret Service says it closed its investigation into the bag of cocaine that was found July 2 in the West Wing -- and, absolutely stunningly, they've been unable to identify who left it.
The agency says there was "no surveillance video footage found" that revealed who made the coke drop. Further, the Secret Service says the FBI lab couldn't find any fingerprints or DNA it could use to compare with the "known pool of individuals" ... such as White House staffers.
Interestingly, authorities say the coke was found in a "receptacle used to temporarily store electronic and personal devices prior to entering the West Wing."
You'd think there are security cameras blanketing nearly every inch of the President's residence -- especially in the West Wing, which hosts so many visitors, journalists and staffers each day. If ya buy what the Secret Service is saying here ... that's, apparently, not the case.
The Secret Service says it's closing the investigation "due to a lack of physical evidence."