An independent report has dismantled the Mexican government's investigation into last year's disappearance of 43 students, starting with the assertion that they were burned to ash beyond identification simply never happened.
The report - released on Sunday - said the students, who were hijacking buses for transportation to a demonstration, may have unknowingly interfered with a drug shipment on one of the buses, prompting a violent reaction on September 26.
"This report provides an utterly damning indictment of Mexico's handling of the worst human rights atrocity in recent memory," Jose Miguel Vivanco, Americas director at Human Rights Watch, said in a statement on Sunday.
"Even with the world watching and with substantial resources at hand, the authorities proved unable or unwilling to conduct a serious investigation."
Iguala, the city in southern Guerrero state where that attacks took place, is known as a transport hub for heroin going to the United States, particularly Chicago, some of it by bus, the report said.
"The business that moves the city of Iguala could explain such an extreme and violent reaction and the character of the massive attack," according to the report, which the experts presented in a press conference.
The report means that nearly a year after the disappearance, the fate of 42 of the students remains a mystery, given the errors, omissions and false conclusions outlined in more than 400 pages by the experts assembled by the Inter-American Human Rights Commission.
The team interviewed witnesses and detainees and reviewed the government's evidence and conclusions. A charred bone fragment of only one of the 43 has been identified and it was not burned at the high temperature of an incineration, contrary to Mexican investigators' claims.
It recommends that authorities rethink their assumptions and lines of investigation, as well as continue the search for the students and investigate the possible use of public or private ovens to cremate the bodies.
The international team of experts, including lawyers, former prosecutors and a medical doctor, says the government investigation was wrong about the nature of and the motive for the attacks.
The report is an indictment of Mexico's investigative procedures and conclusions, and cites key evidence that was manipulated or that disappeared.
Federal police and military were aware of the shootings and present at some of the crime scenes, according to the report. While their involvement is unclear, at the very least they failed to intervene to stop a widespread attack on unarmed civilians.
Government officials did not provide an immediate reaction to the report. The independent team of experts has asked to extend its investigation two more months, but the Mexican government has yet to approve the extension.