Parents of 43 missing students marked the six-month anniversary of their disappearance Thursday by marching to the federal elections office in Mexico City to ask that elections scheduled for June in the southwestern state of Guerrero be suspended.

Dozens of protesters, including some of the missing students' parents, delivered a letter to the elections office asking that the June 7 voting not move forward because people could be voting for politicians tied to drug trafficking, as was the case with former mayor of Iguala, Jose Luis Abarca, who remains in custody.

The students from a rural teachers college were last seen in Iguala. Federal investigators say local police handed the students over to a drug gang, which killed them and incinerated their remains. Nearly 100 people have been detained in the case.

Only one victim's remains have been identified, however, and parents of the young men have continued to demand answers about the events of Sept. 26.

"We came to tell authorities and the Mexican government that as parents we cannot allow the elections," said Meliton Ortega, parent of a student. "They have been six months of torture, of suffering for us."

Students from the Rural Normal School at Ayotzinapa went to Iguala on Sept. 26, to collect money and hijack buses — a common practice — so that they could attend upcoming commemoration events in Mexico City. But police confronted them in Iguala, firing on the buses. Six people were killed.

Federal investigators determined that the police turned the students over to members of a criminal organization who took them to a remote garbage dump near the town of Cocula, killed them, burned the bodies and threw the remains into a river.

Parents and supporters also planned a march later Thursday in Mexico City.