NPS said they believe the missing fossils were formed about three to five million years ago by the tracks of mammals and birds near what used to be a lakeshore.
Scientists visit the area of Death Valley regularly, photographing and recording the exact location of each footprint, NPS said in the statement, and noticed the fossils were missing during a recent trip.
The scientists then alerted park rangers about their discovery.
"It’s illegal to collect fossils, rocks, or anything else in National Parks," Park Superintendent Mike Reynolds says in the statement. "The purpose of National Parks is to conserve the landscape and everything it contains for the next generation. I ask that visitors come and enjoy all there is to see, and to leave it unimpaired for others to enjoy."
NPS has an Investigative Services Branch, and park officials are asking for anyone with information about the fossils to come forward with information.
Investigators believe that a group of men who were photographed near the site may have information about the fossils. They are offering up to $1,000 for information leading to the identification, arrest and conviction of those responsible.