Mexican authorities looking for 43 students missing since late last month have found another mass grave, according to prosecutors.
The students went missing in the town of Iguala and the mass grave was located in the nearby town of Cocula.
Previously, a mass grave found containing 38 bodies was found near Iguala.
However, tests on 28 of the sets of remains showed they were not those of the students.
Meanwhile, two drug gang members were arrested yesterday on suspicion of direct involvement in the disappearance of the 43 students over a month ago, Mexico's top prosecutor said.
Authorities detained four Guerreros Unidos members, two of whom are believed to have helped carry out the crime that has shocked Mexico, Attorney General Jesus Murillo Karam said.
A total of 56 people have now been arrested in connection with the abduction of 43 male teacher college students in crime-plagued Guerrero state.
The students went missing after an attack by police and Guerreros Unidos cartel hitmen in Iguala that also left another six of their classmates dead and 25 wounded on 26 September.
Authorities still have not located the students.
Murillo Karam said the four arrested yesterday were the first to have confessed that they took part in the "abduction and ultimate fate of this large group of people".
"Today, we have the people who carried out the abduction of these individuals," he told reporters.
He said the other two detained yesterday apparently were involved as lookouts for the cartel.
President Enrique Pena Nieto, meanwhile, said he had met in Mexico City with Guerrero's new interim governor Rogelio Martinez.
The president said all public safety agencies would meet with Mr Martinez and work on "measures to restore order and bring back public safety".
Federal authorities accuse on-the-run Iguala mayor Jose Luis Abarca of ordering the attack to prevent the students from disturbing an event held by his wife as president of the local child protection institution.
