The FBI did not immediately respond to queries from the Associated Press but gave the Independent a statement saying "partial remains of an infant child" were found in the Ganado area.
The statement said cause of death wasn't known but that authorities had information that they hoped would lead to "a rapid resolution to the investigation."
Ganado, which is a certified chapter of the Navajo Nation Government, is about 4.5 hours northeast of Phoenix in Apache County, not far from the Arizona-New Mexico border. As of the 2010 U.S. Census, about 1,200 people call Ganado home.
The Navajo Nation is comprised of nearly 27,000 square miles in northeastern Arizona, southeastern Utah and northwestern New Mexico. It is the largest holding of land by Native American tribe in the country.