Three Aztec, N.M., residents have pleaded guilty to excavating, damaging and removing artifacts from an archaeological site in northwestern New Mexico. An investigation resulted in the recovery of an intact Navajo ceremonial mask and portions of two other masks. The intact mask, estimated to be at least 900 years old, is considered priceless by the Navajo tribe because of its cultural value, U.S. Attorney Norman Bay said in a news release. The U.S. attorney's office, reported that Donny Montgomery, 21, pleaded guilty June 19 to unauthorized excavation, removal, damage or alteration of archaeological resources resulting in more than $500 in restoration costs. Chad Cole, 23, and Casey Price entered guilty pleas to unauthorized excavation, removal, damage or alteration of archaeological resources resulting in less than $500 in restoration costs. The three admitted excavating and damaging artifacts on public land near here known as the Hart Canyon Rock Shelter. The incident took place on Feb. 17, 1996. Montgomery faces a maximum penalty of two years in prison and a $250,000 fine. Cole and Price face up to one year in prison and a $100,000 fine.