It came after he was concerned they were to interrupt a speech by his wife

Mayor allegedly demanded that the police 'taught a lesson' to the students

So far 70 people have been arrested including the former mayor and his wife

Gang members waded into the ashes to remove remaining teeth and bone

Some of the fires lasted more than 15 hours according to eyewitness reports

Gang members in Mexico have admitted to massacring 43 students who went missing in September after the local mayor demanded they be 'taught a lesson' so they didn't interrupt a speech by his wife.

Attorney General Jesus Murillo said on Friday that three detainees revealed that they set fire to the group - some of whom were still alive - at a rubbish dump near Iguala in the state of Guerrero, close to where the students went missing.

So far, 19 mass graves have been discovered around Iguala and more than 70 people have been arrested.

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The 43 students, pictured, went missing as they travelled to a protest in Iguala, Guerrero State in September

Residents have held demonstrations calling for a full investigation into the fate of the 43 missing students

Jose Luis Abarca, who was previously mayor of Iguala, left, and his wife Maria de los Angeles Pineda right, were found and arrested in Mexico City on Monday and are believed to have masterminded the massacre

Investigators believe that the fires used to dispose of the bodies burned for 15 hours. After the flames died down, it is claimed that gang members waded through the ashes to recover any bone or teeth which may have survived the intense heat.

The 46 students have not been seen since they disappeared near the southern city of Iguala on September 26 after being attacked by police.

Attorney General Jesus Murillo Karam said: 'The high level of degradation caused by the fire in the remains make it very difficult to extract the DNA that will allow an identification.'

The bone fragments are being sent to Austria to a specialist laboratory for DNA testing.

Police allegedly handed the students over to the Guerreros Unidos cartel who are believed to have killed them and disposed of their bodies.

Murillo Karam said there is no evidence the students were involved in organized crime.

Some 74 people have been detained so far in the case.

Authorities say it started when police, under orders of then Iguala Mayor Jose Luis Abarca, opened fire on students who were in Iguala collecting donations and had commandeered public buses.

Jose Luis Abarca, left and his wife Maria de Los Angeles Pineda are believed to have links to the drug cartel

Investigators believe the bodies of the 43 missing students were burned at this rubbish dump

Six people were killed in two confrontations before the 43 students were taken away and allegedly handed over to Guerreros Unidos.

Abarca and his wife, who were captured Tuesday after weeks of being on the run, are among those in custody.

Jose Luis Abarca, who was previously mayor of Iguala, and his wife Maria de los Angeles Pineda were found and arrested in Mexico City on Monday. They are accused of organising the alleged massacre.

Concerned that the group were about to disrupt a speech to be given by his politically ambitious wife, Abarca ordered police to 'teach them a lesson' according to Mexican media reports.

Pineda demanded that police arrest they students when they threatened to ruin a party she was having, and once the police had the students they were then handed over to the gang members.

Prior to this the police also opened fire on the group, killing several before the bodies were burned.

Attorney General Jesus Murillo is seen leaving the prison after speaking with three gang members

Protesters walk with a sign featuring a photograph of the students

Pineda was able to make these demands as she is at the top of the criminal underworld tree in Iguala, and it was believed her speech may have been her announcement of her desire to succeed her husband as mayor.

What's worse, the students had no intention of disrupting Pineda's speech, but were merely travelling through the town on buses they'd hired to take them to Mexico City for a remembrance service in honor of students massacred there in 1968.

There has been and continues to be a massive outcry across Mexico to see that justice is served for this mass murder.

Authorities searching for the students have found a large number of bodies, although Attorney General Jesus Murillo Karam said he would have to wait until the results of DNA tests have been returned before confirming their identities.

He admitted that many of the bodies had been badly burned which will make the process of extracting DNA more difficult.

He said: 'I have to identify, to do everything in my power, to identify, to know if these were the students.'

Some parents of the missing students do not believe that their children are among the dead.

Mario Cesar Gonzalez told CNN: 'We are not going to believe anything until the experts tell us: You know what? It is them.'

Isrrael Galindo, claimed: 'The government is trying to resolve things its way so that to rid itself of this great problem it is facing. My son is alive. My son is alive. My son is alive.'

The victims were mostly in their 20s studying to be teachers when they planned to travel to Iguala on September 26 for a demonstration.

Protesters have been holding regular demonstrations demanding the safe return of the missing students

Locals have lost faith in the Mexican government and their ability to investigate incidents such as this

Some of the families are unwilling to accept that their relatives are dead until they receive conclusive proof

Amnesty International has criticised the Attorney General over his handling of the case.

Erika Guevara Rosas, Americas Director of Amnesty International said: 'Tragically, the enforced disappearance of these student teachers is just the latest in a long line of horrors to have befallen Guerrero state, and the rest of the country.

'The warning signs of corruption and violence have been there for all to see for years, and those that negligently ignored them are themselves complicit in this tragedy.'

Amnesty said the mayor of Iguala has long been suspected of criminality and links to drugs cartels.

Ms Guevara Rosas said: 'If the allegations against Iguala’s mayor and the federal and local police had been investigated when other serious human rights violations occurred, it is more than likely that the terrible murders and enforced disappearances of the students would not have taken place.'