The United States Department of Agriculture issued a notice Tuesday urging anyone who receives a mysterious packet of seeds in the mail not to plant them and contact their state plant regulatory official for further instructions. Mysterious seed packets appearing to have been sent from China have been cropping up in mailboxes across the country. Government officials are investigating the packets, but do not yet know what they are. “At this point in time, we don't have enough information to know if this is a hoax, a prank, an internet scam or an act of agricultural bio-terrorism,” Agriculture Commissioner Ryan Quarles said. “Unsolicited seeds could be invasive and introduce unknown diseases to local plants, harm livestock or threaten our environment.”