A large box, covered in holiday wrapping paper and addressed to Mnuchin, was left outside the home of one of his Bel Air neighbors Saturday evening, ABC 7 News reported.
The package was labeled as being from “the American people,” according to the news station.
Secret Service agents and Los Angeles police, including bomb-squad officers, soon swarmed the area to investigate the package.
In video of the scene taken by an NBC Los Angeles helicopter, an officer can be seen opening the box, dumping out its contents and spreading a dark, unevenly clumped substance across the ground.
The substance ended up being horse manure, police said. And, according to aerial footage, there was a lot of it.
Afterward, at least three officers could be seen standing around the pile, shining flashlights on the manure and moving it around with their feet, presumably to check whether anything else might be hidden in it.
The LAPD told local media on Saturday that the Secret Service is taking over the investigation. The Secret Service said Sunday that it was “aware of this matter” but referred all questions back to Los Angeles police.
The Bel Air neighborhood is filled with multimillion-dollar mansions and is home to many celebrities.
One resident, Prince Frederic von Anhalt, told CBS Los Angeles that he was blocked from leaving his neighborhood for about two hours while police cleared the scene.
“We have $50 million homes and we can’t move. We can’t get out,” von Anhalt, an entrepreneur and husband of the late actress Zsa Zsa Gabor, told the news station Saturday night. “That’s bad. They have to find another way.”
It is unclear whether Mnuchin was home during the incident. Representatives for the Treasury Department did not immediately respond to requests for comment Sunday morning.
According to the LAPD, its bomb squad handles more than 1,000 calls potentially related to bombs every year. Of those calls, about 22 percent actually involve live devices, live military ordnance or illegal explosives.