Ciudad Juarez, Mexico ? Authorities are calling the arrest of a man in Denver a “major break” in the investigation of the killings of more than 100 young women in a U.S.-Mexico border town.

U.S. Ambassador Tony Garza said the arrest of Edgar Alvarez Cruz on immigration violations in Denver would aid investigators probing the unsolved deaths in Ciudad Juarez, across from El Paso, Texas.

Mexico Atty. Gen. Daniel Cabeza de Vaca said Alvarez Cruz had been under investigation but fled the country before his arrest Tuesday.

The U.S. Embassy said Alvarez Cruz might have been involved in 10 killings as part of a gang.

Many of the victims were dumped in the desert outside Ciudad Juarez and their slayings provoked outrage around the world. Many of the victims were young women last seen in the city’s downtown or after taking buses. Their bodies often didn’t appear until months later.