Packets of unidentified seeds have been turning up, not just in the US, but also in Europe, Canada and the UK.
Authorities in three states are investigating why people have been receiving mystery seed packets from China.
Scientists are trying to determine how it was possible to grow seeds that were tens of thousands of years old.
In a world first, seeds carried to the Moon aboard China's Chang'e 4 spacecraft have actually started to sprout.
Norway's Svalbard depository enables the storage and research of seeds from all over the world.
The number of seeds stored in Norway's "doomsday" seed vault are continuing to grow with hopes of preserving over 100,00...