Mexico City, October 7 (RHC)-- The Mexican government has sent federal police to take over security in a city in the southern state of Guerrero following the disappearance of 43 students and the discovery of a mass grave with dozens of burned bodies.

The students, who are from a rural teacher’s college, have been missing more than a week after police and unknown gunmen ambushed their buses near the small city of Iguala, where they had gone to solicit donations for their school.

Twenty-two police officers have been detained, and the city’s mayor and police chief appear to have fled rather than face questioning. The police have been accused of collaborating with a drug gang called Guerreros Unidos.

Mexican President Enrique Peña Nieto has vowed to bring the perpetrators to justice. Meanwhile, the families of the missing students have continued to protest the government, saying officials are not doing enough to find their loved ones.