MEXICO CITY (AP) — Mexican federal officials rescued 35 people who had been kidnapped for ransom in the southern state of Guerrero, the federal Attorney General’s Office said Wednesday.

Authorities located the victims as part of an investigation to find four people who went missing in Guerrero in October, the office said in a statement

Federal investigators aided by marines also arrested four suspected kidnappers and are seeking the arrest of six more.

The kidnap victims were given medical and psychological attention because they showed signs of severe malnutrition and had injuries from being kept in inhumane conditions by their captors, the office said.

The criminal group that kidnapped the 35 people has a presence in the towns of Apaxtla, Arcelia, Cocula and Teloloapan. Authorities didn’t identify the gang.

In the nearby city of Iguala, Guerrero state authorities found several graves containing nine bodies, officials said. State prosecutors said in a statement that investigators found the graves Wednesday in the neighborhood of Lomas del Zapatero after receiving an anonymous tip.

Last month, police found the bodies of nine other people in San Miguelito, another Iguala neighborhood.

The Pacific coast state of Guerrero has seen a surge of violence in recent years that authorities attribute to drug cartels.

Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.