( CNN ) -- Nearly 5,000 cave paintings found in northeastern Mexico were made by at least three groups of hunter-gatherers who lived in an area previously thought to have been uninhabited , archeologists said . The drawings were discovered in 2006 in a number of caves in the San Carlos mountain range near the modern-day town of Burgos , about 100 miles south of the U.S. border . The first findings about the red markings that depict people , shapes and designs were revealed this week at a conference in Mexico City . Mexico 's National Institute of Anthropology and History has been cataloging and studying the drawings for the past two years . Archeologist Martha Garcia Sanchez said the paintings include human and animal shapes , and relate to astronomy . They 're abstract in nature , she said . `` Their importance is that based on them , we have been able to document the presence of pre-Hispanic groups in Burgos , where before it was believed there was nothing , when in reality it was inhabited by one or several cultures , '' she said . Burgos is in Tamaulipas state , which borders Texas . The ages of the cave paintings remain uncertain for now because archaeologists have not found any objects in the area that could help date them , said another archeologist , Gustavo Ramirez . Rains have also swept away sediment in the area , making that method of dating unavailable , too , he said . At least three nomadic hunter-gatherer groups -- the Guajolotes , Iconoplos and Pintos -- are believed to have made the 4,926 drawings . The images indicate that the groups prioritized hunting , fishing and gathering , Garcia said . Other drawings appear to depict religious and astronomical themes , she said . Drawings of what appear to be teepees , local plants and animals like deer , lizards and centipedes can tell researchers about how the populations lived . Drawings in one cave depicted an atlatl , a pre-Hispanic hunting tool that had not been previously found in other cave art in this part of Mexico , Garcia said . Little is known about the indigenous groups that lived in the mountains near Burgos , she said . These groups evaded Spanish colonists for nearly 200 years , she said , because they had the means to survive in the mountains , where the Spanish would n't venture .
Nearly 5,000 cave painting were discovered in northeastern Mexico in 2006 . This week , archeologists revealed their initial findings . The ages of the paintings are still not known . But they are believed to have been made by hunter-gatherer tribes .