IGUALA DE LA INDEPENDENCIA - Mexican prosecutors were investigating whether local police officers were involved in the disappearance of 57 students who vanished after deadly incidents in the southern state of Guerrero.

Inaky Blanco Cabrera, the state’s chief prosecutor, said the military and state police have been searching for the students - on the ground and by helicopter - since the mass disappearance was reported on Sunday. The students disappeared following a bout of violence in the town of Iguala late Friday and Saturday that left six people dead and 25 wounded in different parts of the municipality.

Authorities say another two died after municipal police fired at buses that were seized by students protesting discriminatory hiring practices.

 State authorities detained 22 municipal officers, including 16 who are believed to have fired their weapons. In all, investigators questioned 162 officers. ‘It’s undeniable that excessive use of force took place,’ Blanco Cabrera told reporters in Acapulco, adding that there was ‘no justification for the use of firearms.’

The officers denied attacking the students, while three said they fired in the air, he said. He added that authorities are investigating whether ‘forced disappearances’ took place, a term used for the abduction of people by security forces. Traffic cameras caught civilians in the back of a municipal police car while a witness said students were seen in the town’s jail cells, he said.

Authorities are also investigating whether an organized crime group was involved in the other shootings because some unidentified gunmen wore dark clothes and masks and drove black sport-utility vehicles. The town of 140,000 people appeared calm on Monday, as shops and schools operated normally while military vehicles patrolled the streets. Soldiers and state police manned checkpoints on the three roads leading to Iguala. ‘We heard about the shootings but people are calm, without fear,’ said newsstand owner Rufina Mendez.