Mexico's President Enrique Peña Nieto delivers a message a
Mexico's President Enrique Peña Nieto delivers a message a

Mexico's president says there is "no place" for impunity in the disappearance of 43 student protesters, a case that implicates police officers and gang members.

Enrique Peña Nieto held a press conference Monday to address the country two days after a mass grave was found in the state of Guerrero. A chief prosecutor has linked the burial site to the case, but investigators are awaiting DNA confirmation.

Calling the disappearances "outrageous, painful, and inacceptable," Peña Nieto said the people of Mexico and the families of the missing "have every right to demand an explanation of the facts, and [demand] justice, that those responsible be found, and that impunity have no place here."

A Mexican prosecutor says two gang hitmen have confessed to helping local police kill 17 of the student protesters who disappeared 10 days ago.

Officials found 28 bodies in a mass grave in the city of Iguala on Saturday, a week after a police opened fire on buses carrying the students from a rural Aytozinapa teacher-training college, under circumstances that remain unclear. More than 100 bullet casings were found near the buses.

Guerrero's chief prosecutor Iñaky Blanco Cabrera said it would take at least two weeks to determine whether the charred remains belong to some of the missing students.

The gang members told officials that dozens of Iguala police officers belong to the Guerreros Unidos, an organized crime group in the area.

Authorities detained 22 police officers and issued arrest warrants for the town's mayor and security chief shortly after the confrontation on September 26 and 27.

Mexico is under heavy international criticism for allowing security forces to commit human rights violations, including torture and extrajudicial killings, with relative impunity.

On its Facebook page Monday, the Escuela Normal Rural Raúl Isidro Burgos, also known as the Escuela Normal Rural de Ayotzinapa, pleaded for the safe return of its students.

"We demand the return of our boys alive, and that justice is done," the school posted.