Tests have identified the remains of one of 43 students who disappeared in Mexico on Sept. 26, an anonymous source told NBC Saturday.

The 43 students, from a teachers college near Iguala, in Guerrero state, were abducted while en route to a protest and were then handed over to drug henchmen.

Since then 12 mass graves have turned up in the region, but the bodies did not belong to the students, who the government said were incinerated and dumped in a river. 

The remains that were used to confirm the identity were from ashes and charred pieces of bone found near a trash dump in southern Mexico, according to Fusion.

The attack has garnered attention in the U.S. and shines a light on the systemic corruption in the country, and many say this isn't the first of this kind of attack.

Thousands marched in Mexico City on Saturday to protest President Enrique Pena Nieto, who is facing criticism of his government's handling of the probe.

Soon after the disappearance, and when the first mass grave were found, at least 22 police officers from the town were arrested, and a few admitted to the chain of events. They admitted to handing the college students over to the drug gang.

The order to do so allegedly came from the town's mayor, Jose Luis Abarca, who claims it was a move to protect his wife who was the target of the protests, according to BBC.

The students were protesting increases in fees and policies affecting the college. Abarca and his wife were detained on Nov. 4, and many at the time believed the capture meant they would find the students.

"If these disappearances and executions have grown over the years, it is because the authorities have permitted this to happen," Itzel Silva, a 38-year-old human rights lawyer, told NBC. "People are fed up with impunity."