None of the remains has been connected to the youths who disappeared after a clash with police in the city of Iguala on Sept. 26, and authorities do not believe any will be.
Prosecutors say the students were turned over to a drug gang that killed them and incinerated their bodies in a case that has put attention on the huge number of people who have gone missing in Guerrero and other Mexican states where drug violence is widespread.
Federal authorities began turning up unmarked graves after beginning an investigation into the disappearance of the 43 young men following the confrontation between students and police that resulted in six confirmed deaths in Iguala, a municipality of 120,000 people 200 kilometres (160 miles) south of Mexico City.
More than 20,000 people are listed as missing across Mexico, and there are many "disappeared" in Guerrero, a state that is a major opium producer and the battleground among several cartels warring over territory and drug smuggling routes.
Many people are questioning the government's version of happened to the students, including parents and the National Human Rights Commission, which last week issued a report outlining at least 30 omissions in the investigation that would help determine the youths' fate.
Some were very basic investigation procedures that were never performed.
Yesterday, a few hundred people led by parents of the missing youths marched in Mexico City to call for justice in the case. Demonstrations have been held on the 26th of each month since the incident.
