Security forces investigating the role of municipal police in clashes in this southern city a week ago found a mass grave on the edge of town, raising fears the pits might hold 43 students missing since the violence that also resulted in six shooting deaths.
Guerrero Gov. Angel Aguirre said the victims had been "savagely slaughtered."
Jesus Lopez, the father of one of the missing students, told The Associated Press that a delegation of family and school representatives would come to Iguala on today to get information about developments in the case from authorities.
"We cannot say anything. We are very nervous, but until they inform us, there is nothing," said Lopez, whose 19-year-old son, Giovani, hasn't been seen since the violence last weekend.
Separately, a group of students and relatives of the missing young people said they planned to march today from Aytozinapa Normal school to the state capital of Chilpancingo to demand information in the case.
Anger over the discovery of the graves exploded Saturday night when a group of young people from the school protested outside the governor's Chilpancingo residence.
They threw Molotov cocktails and overturned a car after state authorities told them they would not allow them to travel to the graves to determine if the bodies are those of their missing classmates.
Guerrero State Prosecutor Inaky Blanco did not say yesterday night how many bodies were in the burial pits uncovered on a hillside on Iguala's outskirts, and he declined to speculate about whether the dead were the missing students.
"It would be irresponsible" to jump to conclusions before tests to identify the bodies, Blanco said. Officials said the federal Attorney General's Office and the National Human Rights Commission had sent teams of experts to aid state authorities in identifying the remains.
About 100 soldiers, marines and federal and state police on Saturday cordoned off the area where the grave site was found in the poor Pueblo Viejo district of Iguala, which is about 200 kilometers south of Mexico City.
Blanco said eight more people had been arrested in the case, adding to the 22 Iguala city police officers detained after a police confrontation with student protesters last weekend set off a series of violent incidents in the city.
The prosecutor has said state investigators had obtained videos showing that local police arrested an undetermined number of students after the initial clash and took them away.
He said some of the eight newly arrested people were members of an organised crime gang, adding that some of them had given key clues leading to the discovery of the mass grave.
