Police have captured four suspects in the kidnapping and killing of the daughter of Mexico's former sports commissioner, a case that provoked huge protests against crime and police incompetence.

Among those arrested is Candido Ortiz, accused of leading the kidnapping band "the Reds" and organizing the abduction of 19-year-old Silvia Vargas, Public Safety intelligence coordinator Luis Cardenas said Tuesday.

Ortiz's voice identifies him as the one of the negotiators who demanded a ransom from Nelson Vargas, Mexico's top sports official until 2006, Cardenas said. He was captured along with his brother and two others in the Gulf coast state of Veracruz.

Another brother is a former driver for the Vargas family who was arrested last year. Still at large is a fourth brother who has escaped twice from police custody.

Vargas was apparently snatched from her vehicle as she drove to school in Mexico City in September 2007. Her captors initially demanded a ransom, then abruptly stopped making contact.

With their daughter still missing, the Vargas family went public with the case a year later. Her body was found in a clandestine grave in December 2008.

The arrests come two weeks after federal police announced the capture of two suspects in another prominent kidnapping case in which the 14-year-old son of a sporting goods magnate was slain.

Those arrests, however, raised more questions about police efficiency: federal investigators say one of the suspects confessed to killing Fernando Marti — but said he did not know the suspects arrested a year ago by Mexico City police.

Authorities say they are trying to sort out the confusion.

The Vargas and Marti cases helped ignite nationwide protests last year against Mexico's wave of kidnappings. The government says police are increasingly capturing kidnappers, but Mexico's abduction rate remains one of the world's highest.

The Mexican government says there are about 97 kidnappings a month, but most abductions go unreported due to widespread fear that police themselves may be involved. The nonprofit Citizens' Institute for Crime Studies estimates the real rate is closer to 500 a month.