Mexico City, October 14 (RHC-Xinhua) -- Some 20 members of an Anti-Kidnapping Tactical Force have been arrested for opening fire Sunday on a van full of students, the Attorney General's Office for Mexico's southern state of Guerrero (PGJE) said Monday.

Deputy Attorney General Victor Leon Maldonado of the Guerrero State Prosecutor's Office told reporters at a press conference that the arrested police officers were involved in an operation to find suspected kidnappers when the incident occurred.

The officers had set up check points around the state capital Chilpancingo, and the van had been ordered to stop at one of the check points but failed to do so. The officers said they had also heard the sound of a weapon being fired.

The officers then fired on the van's tires, accidentally hitting one of the passengers, who turned out to be a German national, according to the police version.

The van stopped and the police inspected the vehicle, discovering it was full of students from a local university, who were coming from the Pacific coast resort of Acapulco. The injured German student was taken to a private hospital whose doctors said his condition was stable.

The PGJE said they were investigating the incident, which occurred less than a month after 43 students went missing on September 26th following clashes with police in the Guerrero town of Iguala.

The whereabouts of the students in that case are still unknown, although forensic experts are trying to determine identities of bodies uncovered at about 10 mass graves found around Iguala, and 26 police officers are under investigation.