In a Facebook post, the Gallatin County Sheriff's Office said a man was hurt recently near Yellowstone National Park looking for the Forrest Fenn treasure chest.
Nearly a decade ago, author and art dealer Forrest Fenn said he hid a chest with gold and other valuables worth at least $2 million.
Since then he has provided several clues to help people find the chest.
Many believe it's somewhere in the Rocky Mountains.
The sheriff's office said that in recent years, at least two people have died and two others have been rescued near death while searching near Yellowstone.
The sheriff advises treasure hunters to give someone their exact location before going out, be prepared for changing weather and the possibility of wildlife encounters.
People should also plan for a lack of cellphone service.