On Tuesday, Mexican prosecutors announced that an Austrian forensics lab has been unable to find anymore DNA to identify the burned remains that may belong to 43 missing college students.

According to The Associated Press, the Attorney General's Office said the University of Innsbruck lab reported "excessive heat" damaged mitochondrial DNA in teeth and bone fragments.

Only 16 sets of remains were sent to the lab as the others are too damaged to be identified.

The lab says conventional techniques to identify the students will not work. They plan to use a method called massively parallel sequencing as a last ditch effort. There is a risk, however, that these tests may destroy the samples without identifying the remains or providing any information. It may take an additional three months to gain any answers through this testing.

"The main risk is that the DNA extracted may be destroyed," University of Innsbruck said according to prosecutors.

Previously, DNA was found in a set of the remains belonging to one of the 43 students.

According the Vidulfo Rosales, the lawyer representing the students' families, the parents were not notified prior to the remains being sent to the lab.

"If these tests are done on the bone fragments, there could be practically nothing left," Rosales told media. "This is going to have an impact on the parents' belief system ... In rural tradition, mourning is highly symbolic, highly important."

The 43 students disappeared on Sept. 26 in the Guerrero state city of Iguala.

According to Attorney General Jesus Murillo Karam, police attacked on orders from Iguala's now former mayor Jose Luis Abarca and his wife, Maria de los Angeles Pineda Villa.

Prosecutors believe Villa thought the students planned to protest her speech and ordered police to prevent their disruption. Police are believed to have opened fire on the students as they were travelling to the area in buses. In the confrontation, three students and three bystanders were killed.

According to prosecutors, the students were turned over to a drug gang, Guerreros Unidos, and they were later killed and their bodies incinerated. The burned remains were then allegedly crushed and thrown in a river.

The students appeared to have no intention to protest the speech and were on their way to Mexico City for a service honoring students massacred in 1968.

The former mayor and his wife went into hiding after the kidnappings and were found hiding in Mexico City in November and charged.