More graves discovered, security heightened

Extra security officials patrol the streets of Iguala in Mexico as investigations continue into the disappearance of 43 students.

The extra federal officers are here after 22 local police were arrested in connection with the incident and the subsequent discovery of mass graves that contain human remains.

The students went missing after they clashed with police in September. The police and the town's mayor are being investigated, although the mayor has not been arrested.

Officials fear the graves, four more of which were just discovered bringing the total to 10, may contain the remains of the students. Forensic studies are still being conducted.

The involvement of police and government officials in the incident has prompted public outcry and underlines the widespread corruption inside the country's security force.