Mothers of women killed in a string of murders in the Mexican city of Ciudad Juarez have had their first formal meeting with the country's president.
Many of the dead were young, poor factory workers
One mother said President Vicente Fox promised to bring those responsible to justice.
The authorities have been accused of mishandling the investigation.
Many of about 250 women killed in Cuidad Juarez over the past 10 years were factory workers snatched while travelling to and from their jobs.
"Fox gave his word... that the investigation was going to get to the bottom of these crimes," said Norma Andrade, whose 17-year-old daughter was killed in 2001.
Relatives warned that if progress was not made, they would take their case to the Inter-American Court of Justice.
There have been several arrests - but most cases were allegedly based on forced confessions and only one man has been convicted, for one of the killings.
Another mother said: "The ones they have in jail are innocent, and the ones most responsible for the crimes are those in charge of law enforcement."
The Mexican National Human Rights Commission has issued a report condemning police negligence and denouncing a lack of political will to solve the murders.
The commission called for a special prosecutor to be appointed and for Mexico to request help from the United States Federal Bureau of Investigation.
Rights groups say Mexican authorities are in 'denial'
The murders first came to light in 1993, when bodies of dead girls were found in dusty desert graves and by roadsides in Ciudad Juarez, across the border from the US city of El Paso in Texas.
Many of the dead were poor seamstresses who worked in the city's numerous assembly lines.
Most had been brutally sexually assaulted and tortured before their deaths.
It is not known whether the murders were committed by a serial killer or killers, or if criminal gangs are involved.