The National Park Service is starting to dig out the mouth of an unexplored cave in South Dakota's Wind Cave National Park.

The cave was found in 2004 by the NPS and since then the location of the entrance has been kept a secret. NPS has mounted a proper, scientific excavation of the site with the help of other adventure seekers.

The exploration has already yielded hundreds of bones dating back as far as 11,000 years. There are bones of three living species, which are not previously known to live in the region.

There were bones of pika, which lives in cool mountain climates, as well as the platygonus, an extinct relative of the peccary and pine martin have come from the cave entrance with much left to excavate.

Researchers believe that the exploration of the cave would provide insights on the region's climate change and would also send light into the region's history.

Scientists are scheduled to begin excavating the cave on Monday. The scientists excavating the cave are being led by East Tennessee State University professor Jim Mead. He told the Washington Post that he expects to find 100,000 bones before the end of the summer.

Researchers believe the cave could be very deep because of the direction and speed of winds coming from its entrance. It could even connect, through a blocked or unexplored passage, to Wind Cave one-third of a mile away.