Definition: In this task, you are given a text of many news articles seperated by special token "|||||". Your task is to summarize them.
Input: Image copyright Reuters Image caption The new graves were found in a village outside Iguala 
  
 Four more mass graves have been found near the southern Mexican town of Iguala, where 43 students went missing last month, officials say. 
  
 There is no word on the number of the bodies discovered in pits on Thursday. 
  
 The discovery came during a huge operation to find the students, who disappeared after clashing with police. 
  
 They were last seen being bundled into vehicles. Last week 28 burnt bodies were found in six shallow graves, but have yet not been identified. 
  
 Forensic tests are expected to take weeks. 
  
 Federal Attorney General Jesus Murillo Karam said the new graves also contained burnt bodies and are in the same area as the first set of graves. 
  
 He said the security operation in Iguala, in Guerrero state, had resulted in the arrest of 34 people - mostly local police. 
  
 He said a formal search had now been launched for the town Mayor, Jose Luis Abarca Velazquez, as well as his wife and head of security. They went on leave after the clashes and have not appeared. 
  
 Media playback is unsupported on your device Media caption The mass graves are overwhelming, reports Juan Carlos Perez Salazar 
  
 The students were holding a protest over hiring practices when they clashed with police on 27 September. 
  
 A number of theories about the reasons for their disappearance have been put forward. 
  
 The students all went to a local teacher training college with a history of left-wing activism, but it is not clear whether they were targeted for their political beliefs. 
  
 Some think that they may have angered a local drug gang called Guerreros Unidos by refusing to pay extortion money. 
  
 Others believe there may be a link between the students' disappearance and a speech given by the wife of Iguala's mayor on the day of the clashes. 
  
 She was speaking to local dignitaries in Iguala on the day the incident occurred and some believe the students may have been targeted because it was feared they could disrupt the event. ||||| The case of 43 Mexican students missing since an attack by gang-linked police took another grim turn Thursday with the discovery of new mass graves where suspects said some were buried. 
  
 Four new suspects took investigators to the site of the four pits, 200 kilometers (125 miles) south of Mexico City, but the number of bodies remains unknown, said Attorney General Jesus Murillo Karam. 
  
 "They say there are remains of students," Murillo Karam said, adding that some of the bodies appeared burned. 
  
 The discovery has put another dent on hopes of finding the students alive almost two weeks after they were pursued by Iguala police officers accused of working in tandem with the Guerreros Unidos gang. 
  
 The pits are "relatively" close to the location of another mass grave found last weekend in the southern state of Guerrero that contained 28 unidentified bodies, the attorney general said. 
  
 Two hitmen confessed to executing 17 of the students and dumping them in the mass grave found last Saturday. 
  
 Authorities have said it will take at least two weeks to identify the bodies through DNA analysis. 
  
 The case has outraged Mexicans, who held protests across the country Wednesday to demand the return of the students, in a nation that has lost tens of thousands of people to drug violence since 2006. 
  
  
  
 Protesters hold photographs of missing students outside the office of Mexico's Attorney General (Reuters) 
  
 Authorities say crooked officers shot at buses the students had seized to return home on September 26, sparking a night of violence that left six people dead, 25 wounded and 43 missing. 
  
 Surveillance cameras showed several students being taken away in patrol cars. 
  
 Murillo Karam said there are several lines of investigation into the motive but that the city's mayor, Jose Luis Abarca, his wife and the public security director are wanted for questioning. 
  
 The trio have apparently gone into hiding. 
  
 The mayor's wife, Maria de los Angeles Pineda Villa, is the sister of two late members of the Beltran Leyva drug cartel, which founded the Guerreros Unidos. 
  
 Murillo Karam did not say why the mayor and his entourage were being sought. 
  
 But Mexican media, citing an intelligence services report, say Abarca's wife asked police to confront the students because she feared they would interrupt a speech she was giving that night. 
  
 The mayor then reportedly told the police chief to teach a lesson to the students, who are from a teacher training college known as a bastion of protests. 
  
 The students say they were in Iguala to raise funds, though they had commandeered the buses to return home, a common practice among the radical aspiring teachers. 
  
 Guerrero chief prosecutor Inaky Blanco said authorities did not arrest Abarca before he disappeared last week because he had immunity as mayor, which was only revoked by local lawmakers on Thursday. 
  
 Abarca requested a 30-day leave of absence before vanishing a few days after the attacks. 
  
 Blanco said Abarca faced state charges of negligence for preferring to stay at a party and go to bed instead of stopping the violence. 
  
 The mayor "left the victims at the mercy of public security members," Blanco said. 
  
 Four more municipal police officers have been arrested on homicide charges in the case, in addition to 22 who were detained last week. 
  
 Officials also arrested four alleged members of the Guerreros Unidos gang, which prosecutors say worked hand-in-hand with police during the assault. 
  
 Murillo Karam did not say who the four new suspects were, but their arrest brings the total of detainees to 34. 
  
 President Enrique Pena Nieto deployed federal forces to Iguala on Monday to take over security and disarm the local police. More than 100 officers were sent to a military base for retraining. 
  
 Pena Nieto vowed again on Thursday to punish those responsible for the "act of barbarism" and said he had instructed security officials to accelerate the investigation. 
  
 After Wednesday's nationwide protests, Pena Nieto said "the president is the first to endorse these appeals." 
  
 The Iguala case has embarrassed the mayor's leftist Democratic Revolution Party (PRD), which apologized for allowing him to run for office in 2012. 
  
 Governor Angel Aguirre, who is also a PRD member, has come under fire over the case but has repeatedly rejected calls by protesters to resign. |||||
Output:
Four more "clandestine" mass graves housing burnt bodies have been found in Iguala, Mexico, reports Reuters, and they're "relatively" close to six others discovered last weekend. Four suspects led investigators to the graves yesterday; it isn't clear how many bodies the graves contain, AFP reports. The suspects "say there are remains of students," Mexico's attorney general says. Officials have been searching for some 43 missing students who were last seen hauled into vehicles after clashing with police late last month, the BBC reports. Two men have since confessed to executing 17 students and depositing them in one of the graves found on Saturday. Police are now attempting to identify the victims with DNA samples from students' relatives. Mexican officials have yet to provide a motive for the killings, but as the students attended a teacher's college known for its left-wing activism, some say it may have been a political attack. Others say the murders were carried out by the Guerreros Unidos gang, which wanted extortion money. Yet another theory: that there's a connection between the vanishings and a speech the wife of Iguala's mayor was to give to local dignitaries; the two occurred on the same day, the BBC reports. Officials have now begun searching for fugitive mayor Jose Luis Abarca, his wife Maria de los Angeles Pineda Villa—whose late relatives were part of the Beltrán Leyva drug cartel, which formed Guerreros Unidos—and the local head of security. Some 34 people have now been detained, including 26 police officers who may have ties to gang members.