The US Department of Agriculture is investigating after people across the United States have reported receiving mysterious packages of seeds that appear to have been sent from China.

On Sunday, the Whitehouse Police Department in Northwest Ohio put out a warning following the discovery that the packages had been sent to homes all over the US.

"One of our residents received a package in the mail with Chinese writing and a return address in China. The package was labeled as containing jewelry but was found to have a small bag of what appeared to be seeds. The resident did not order any such item and contacted our office," the department wrote in a Facebook post.

"The investigating officer called the US Postal Inspector's office and learned that similar packages have recently been delivered to various homes across the country. It is not known at this time why these packages have been arriving on US doorsteps."

The department urged that if you receive one of the packages to not open them, as they may be an invasive plant species. Other States put out their own alerts too.

Of course, people couldn't resist having a bit of fun with it.

At least 27 states have put out their own warnings for residents to report similar packages, reports The New York Times. After investigation, the Whitehouse Police Department released an update saying that the seeds could be part of an online "brushing" scam.

"A brushing scam is an exploit by a vendor used to bolster product ratings and increase visibility online by shipping an inexpensive product to an unwitting receiver and then submitting positive reviews on the receiver's behalf under the guise of a verified owner," they explained on Facebook.

The scam improves the seller's rating, making them appear higher in rankings online. 

"Although not directly dangerous, we would still prefer that people contact us to properly dispose of the seeds," they added. Pathogens, contaminates or insects could be hidden within the packaging, for instance, or the seeds themselves could belong to an invasive species. 

The US Department of Agriculture urges anyone who receives a mysterious unsolicited bag of seeds to contact their state regulator and hold onto the package until they are given further instructions.