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Marco Ugarte, Associated Press
Children place candles next to six mock coffins, representing those who died in a police attack in Guerrero state, placed outside the National Palace by protesters in Mexico City, Saturday, Nov. 1, 2014. Relatives of the missing have grown increasingly frustrated at the pace of the investigation of the Sept. 26 police attack in the city of Iguala, that left six dead and 43 missing students. The missing were apparently handed over to a drug gang by city police.

MEXICO CITY — Federal police early Tuesday detained the former mayor of the southern Mexican city of Iguala, who officials say ordered the Sept. 26 attacks on teachers' college students that left six dead and 43 missing.

Jose Luis Abarca and his wife, Maria de los Angeles Pineda, were arrested in Mexico City without resisting, according to two security officials, who spoke on condition of anonymity because they were not authorized to speak to the press. They provided no other details.

The couple was in the custody of the Attorney General's Office, where they were giving statements. More than a month after the attacks, Mexican authorities still have not determined the whereabouts of the 43 students.

Their detention could shed light on disappearances, which have remained a mystery.

The rural teachers college students disappeared after an attack by police in Iguala, which is in the southern Mexican state of Guerrero. Authorities say it was ordered by Abarca, who thought the students were aiming to interrupt a speech by Pineda, and was carried out by police working with the Guerreros Unidos cartel. Authorities say Pineda was an operative in the cartel.

The search for the students has taken authorities to the hills above Iguala, where 30 bodies have been found in mass graves but not identified so far as any of the students. Last week, the search turned to a gully near a trash dump in the neighboring city of Cocula, but still no remains have been identified.