Mexican army holds troops over June killing
Eight Mexican soldiers have been arrested over the killing of 22 alleged gang members in a shooting incident in June in the south-west of the country.
The seven soldiers and their commander are charged with military disobedience and breach of duty.
The arrests came after a witness said most of the victims were killed in cold blood.
The army had said they died in a firefight, but suspicions were later raised as only one soldier was injured.
The confrontation happened on 30 June in the village of San Pedro Limon in the municipality of Tlatlaya, about 240km (150 miles) south-west of the capital, Mexico City.
At the time, the authorities said the victims were probably members of La Familia Michoacana drug cartel.
But some of the bodies appeared to show bullet wounds at chest level, suggesting they had not been killed in a shootout.
Witnesses then said only one person died in the initial confrontation - the others were killed after surrendering to soldiers, our reporter says.
Last week, Mexico's federal attorney-general's office said it had not found evidence to corroborate that account.
Criminal organisations are known to operate in the area, in the southern part of Mexico state. La Familia Michoacana is active in neighbouring Michoacan and Guerrero states.
'War on drugs'
President Enrique Pena Nieto has promised to review the war on drugs policy of his predecessor, Felipe Calderon.
Critics said Mr Calderon's decision to deploy the armed forces to combat the powerful drug cartels in December 2006 had led to a sharp increase in violence.
At least 60,000 people are estimated to have been killed in drug-related violence during his six-year term.
Despite that criticism, Mr Pena Nieto's government has continued to fight the gangs.
In February, it managed to arrest Mexico's most wanted drug lord - Joaquin Shorty Guzman - who had evaded justice for more than a decade.
Correction: A version of this story published earlier on 26 September said a soldier had been killed in the June incident. He was in fact wounded.