The remains were burned and extremely hard to identify, Coahuila state prosecutors' spokesman Jesus Carranza said.
News of the finds came as 12 bodies were unearthed from clandestine graves in the southern Mexico state of Guerrero and about two months after 67 bodies were found in western Mexico.
Such discoveries remain common despite government claims the number of killings has gone down in the past year.
Police in Coahuila have not said whether an organised crime group is suspected over the skeletal remains, but the area is known to be dominated by the violent Zetas drug cartel. Officers have arrested 10 men, including four police officers suspected of aiding a criminal group.
The police operation took place on ranches in 11 different towns around the border city of Piedras Negras, opposite Eagle Pass, Texas, after interviews with relatives.