MEXICO CITY (AP) -- Human Rights Watch called Friday for the Mexican government to fully investigate a supposed shootout in which troops killed 22 suspects while suffering only one soldier wounded.
It is unclear whether there has been any investigation of the June 30 bloodshed at the federal level.
In a statement, the New York-based Human Rights Watch said that nearly two months after the deaths, "there are more questions than answers about what really took place that day."
"A thorough, objective, and independent investigation that examines whether the soldiers acted lawfully, and assesses evidence of state misconduct is needed and required by law," the group's Americas director, Jose Miguel Vivanco, said.
The group said Mexico's federal Attorney General's Office had said it was looking into the case. But when The Associated Press filed a formal request under public access laws for the results of the autopsies, the office said that it did not have the information or that it did not exist.
A spokesman for federal prosecutors could not explain how his office could be investigating the case without having the autopsy results.
State prosecutors whose examiners carried out the autopsies have refused to disclose the results, saying state law prohibited them from releasing the information because it is part of a continuing investigation.
A brief army statement a few days after the killings called the dead "presumed attackers" who opened fire on soldiers first, and suggested they were kidnappers.
The Mexico state prosecutors' office said in a July 15 statement that a chemical test indicated all 22 of those killed had fired weapons.
But the chemical-reaction test used checks only for the presence of lead, and is a usually used by police in other countries to test only suspected bullet holes on clothing, not a suspect's hands. Modern police departments use a clean swab and a scanning electron microscope to identify three "signature" elements of gunfire -- barium, lead, antimony.
Mexico's Defense Department has said soldiers were patrolling in a violent area where drug gangs are active when the patrol came under fire from a warehouse where a gang of 21 men and one woman were hiding. One soldier was wounded, while all of the suspects were killed.
Witnesses described almost two hours of gunfire, though the warehouse where many bodies were found showed little evidence of sustained fighting when visited by AP journalists. About six incoming rounds appeared to have hit the facade, the only part of the building with a window or door where soldiers likely would have been firing at people inside.
At least five spots along the warehouse's inside walls showed the same pattern: One or two closely placed bullet pocks at chest level, surrounded by a single mass of spattered blood, giving the appearance that some of those killed were standing near or against the wall and were hit by one or two well-placed shots.
The incident was the most dramatic in a string of reported battles in which the army says criminals fired first at soldiers who then killed them all, while suffering few or no losses. There have been so many such incidents that human rights groups and analysts have begun to express skepticism about the military's descriptions of the events.
Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.