Mexico will open a new investigation into the disappearance of 43 students in Iguala, who went missing after authorities intercepted them on their way to a protest five years ago.

“We will start again,” Omar Gomez, special prosecutor of the case, said on Wednesday, vowing to “remove all the irregularities … that were committed.”

The alleged abduction and suspected massacre of the students cast a long shadow over the administration of former President Enrique Pena Nieto, which was seen as complacent in its approach to the investigation.

Prosecutors said the students were killed by a drug gang and their bodies incinerated but conclusive evidence was never presented and investigators effectively identified the remains of only one of the 43.

“Unfortunately, it has been five years of feeding lies, we practically prefer to start from scratch because at first everything was done badly,” Felipe de la Cruz, the father of one of the missing students, said in an interview to local media.

Gomez also said authorities were tasked with investigating “a long list of politicians that bear different degrees of responsibilities”.

President Andres Manuel Lopez Obrador formed a commission last year that was tasked with looking into the handling of the case, while an investigation was also opened looking at the officials who were in charge of the investigation.

“The whole government is going to help with this plan and I can assure you that there will be no impunity either in this sad and painful case or in any other,” said in December.

Suspects released

A judge this week ordered the release of 24 local police officers arrested in connection with the case, days after Gildardo Lopez Astudillo, the man suspected of ordering the killing, was released. The judge said the suspects were tortured while in custody.

So far 77 of 142 suspects detained have been released by courts. Earlier this month, Deputy Interior Secretary Alejandro Encinas accused authorities of fabricating evidence and using torture to benefit the perpetrators of the crime.

In a private meeting earlier this week, Obrador told the relatives of the victims that he was working on preventing the release of more suspects.

Last year, the UN’s human rights office said their office had strong evidence to believe some of the people arrested in connection with the investigation were arbitrarily detained and tortured.