Many of the victims were young and poor 'with no power in society'
Human rights group Amnesty International has accused Mexican police of negligence and fabricating evidence in their investigation of hundreds of sex killings of young women.
More than 370 women have been murdered - a third of those raped - in the last decade in the rough border city of Ciudad Juarez, says the London-based group.
Judicial officials have blamed drug traffickers, domestic violence and serial killers but police and prosecutors are in a "culture of denial", says Amnesty.
The organisation's report found that the authorities had misidentified bodies, mishandled evidence and failed to catch the real killers.
"Clearly there has been fabrication of evidence," said Amnesty's Secretary General Irene Khan at a Mexico City news conference.
"There has been mismanagement of cases and failure to follow up leads."
She met President Vicente Fox and other political leaders to press the government to take a larger role in the investigations and reform Mexico's justice system.
Speaking afterwards, Mr Fox said greater co-operation from all levels of government was being pursued in trying to find those responsible for the killings.
An Amnesty investigation found that many of the victims in the cities of Ciudad Juarez and Chihuahua were "young, poor women with no power in society, whose deaths have no political costs".
They were students or retail employees, snatched off the street and sexually assaulted, strangled and abandoned in the deserts on the outskirts of the cities.
Families of the victims say many of the women were abducted and held captive for several days and some were tortured.
Norma Ledesma, the mother of a 16-year-old girl found dead in Chihuahua City last year, said she had no confidence in the state police.
"None of the culprits have been caught. The people they have in jail are innocent," she said.
Amnesty has accused officers of torturing people into confessing and building a case around that. The group also says 75 bodies are still waiting to be identified.