A man suspected of involvement in a 13-year wave of rapes and killings in a Mexican town that left more than 300 women dead has been detained in the US.
Mr Alvarez Cruz was held in Denver on immigration charges
Edgar Alvarez Cruz was arrested for alleged immigration violations in Colorado and faces extradition.
The US embassy said he may have been part of a gang involved in the case.
The women were abducted, often sexually assaulted or raped and then murdered in Ciudad Juarez on the Texan border. Many bodies were dumped in the desert.
The US Ambassador to Mexico, Tony Garza, said it was a major breakthrough in the case.
There have been several arrests over the years and the murders have been variously attributed to serial killers, drug cartels and domestic violence.
Several gangs have also been mentioned as the perpetrators.
But there was no major breakthrough and last year Amnesty International accused the federal government of not doing enough to stop the killings.
Many of the victims were poor women employed in factories in the industrial city.
The BBC's Duncan Kennedy in Mexico City says Mr Alvarez Cruz had been under investigation but left Mexico before he could be captured.
Mr Garza said Mr Alvarez Cruz would be extradited to Mexico as soon as possible.
Mexican Attorney General Daniel Cabeza de Vaca said: "We don't exactly know how many homicides he may have been responsible for but there is solid evidence in several cases that we know of."