A judge in Mexico has ruled that there is not enough evidence to try four of the seven soldiers who have been charged with executing 22 gang suspects after they surrendered.

The officer and three soldiers, who were involved in the deadly 2014 confrontation near the village of San Pedro Limon in Mexico state, still face lesser charges and will remain in prison for now.

The BBC reports the judge ruled there was still evidence enough to continue the trials of the three other soldiers who allegedly performed the executions.

Mexico’s human rights commission found that 15 corpses of the 22 people killed displayed signs that they had been shot after surrendering. Defensive wounds on several of the bodies suggested that they had been fired on while unarmed.

Last year, the BBC reported Mexico's Attorney General Jesus Murillo Karam, who stepped down from his position in February, said that the soldiers involved in the June slaying opened fire "without any justification whatsoever."

Mexican human rights activists have accused high-ranking army officers of giving written orders that encouraged soldiers to kill suspected members of criminal groups in night-time operations.

An investigation into the deaths of the 22 suspected gang members in San Pedro Limon revealed a document dated 19 days prior to the killings, which detailed operational orders regarding strategies for taking down criminal gangs.

According to the Guardian, one of the orders read that, “The troops should operate at night en masse, while reducing their activity during the day, in order to take down criminals when it is dark.”

According to the Miguel Agustin Pro Juarez Human Rights Center, “This is the first time that express orders have been documented that would encourage the commission of serious human rights violations.”