The leader of a Mexican drug gang suspected in the disappearance of dozens of college students last month killed himself Tuesday after a gun battle with federal police, authorities said.
Mexico's attorney general later said that 28 bodies discovered in a mass grave do not belong to any of the students, who disappeared after a confrontation with police in the city of Iguala.
The whereabouts of the 43 missing students are still unknown, said Atty. Gen. Jesus Murillo Karam, adding that authorities also do not know the identities or fate of the people found in the grave.
Dozens of police officers from Iguala and the nearby town of Cocula have been arrested and reportedly have admitted to taking part in the abduction of the students. Prosecutors allege that police abducted the students and then leaders of Guerrero Unidos cartel ordered them killed.
Benjamin Mondragon Pereda, leader of the cartel, shot himself early Tuesday after being surrounded by police in Jiutepec, a city in Morelos state, said Gonzalo Ponce, a spokesman for the Mexican government.
Authorities said Mondragon first negotiated for the safe exit of a pregnant woman he was with at the time.
"When he saw that there was no escape, he shot himself," Ponce said.
Prosecutors accuse Mondragon's gang, which is believed to specialize in the transport of marijuana and heroin to Chicago, of working with local authorities on the night the 43 freshmen from a rural teaching college went missing.
Guerrero state prosecutor Inaky Blanco said the students had attended a demonstration in Iguala that turned violent when police opened fire on protesters, killing six. Afterward, Blanco said, dozens of students were apparently detained by police. They were then probably ordered killed by cartel leaders, he said.
Several mass graves have been discovered in the area. The mayor of Iguala, who is believed to have connections to Guerrero Unidos, has fled town.
The recent events have highlighted the close ties between local authorities and organized crime in towns across Guerrero, one of Mexico's most dangerous states.
On Monday, the mayor of Cocula was arrested along with dozens of local police officers on suspicion of having ties to Guerrero Unidos, according to Mexican media reports.
Protesters angry over the events in Iguala have held violent demonstrations in recent days. On Monday, hundreds of people clashed with riot police and set fire to the Guerrero government headquarters in the state capital, Chilpancingo.
According to local media reports, protesters were gathering again in Chilpancingo on Tuesday afternoon. Some reportedly had come from universities in other parts of Mexico to register their anger at the violence against students.
Over the weekend, authorities in Chilpancingo fired on a van carrying several university students after it failed to stop at a police checkpoint. Officials said police mistakenly believed the van was carrying kidnapping suspects who had killed an officer in an earlier shootout.
One student, a German national studying at the Monterrey Institute of Technology, was wounded.