It could be the break authorities have been looking for in the rapes and killings of at least ten women in a city along the US-Mexican border.
The US ambassador to Mexico says the arrest of a man in Denver is "a major break" in the investigation into the unsolved deaths in Juarez, across from El Paso, Texas.
Edgar Alvarez Cruz was arrested earlier this week on immigration violations.
More than 100 young women have disappeared along the Mexican border since 1993. Many of the victims were young women last seen in downtown Juarez or after taking buses. Their bodies were often found months later, dumped in the desert.
Mexico's attorney general says Alvarez Cruz had been under investigation but fled the country. He says there is "solid evidence" against him in several cases.
The US Embassy says Alvarez Cruz may have been involved in ten killings as part of a gang.