Federal Attorney General Rafael Macedo de la Concha said that at least four other officers, including a commander, were being sought and that more yards in the border city would be dug up in a search for bodies.

"We're looking at six additional homes, and new lines of investigations are coming up,"| Mr. Macedo de la Concha said in Mexico City.

Among the leads that have surfaced, two Mexican federal law enforcement officials told The Morning News, is the possibility that cartel members and state and local police officers may have had a role in the abduction, sexual torture and killing of a string of young women in Ciudad Juárez over the last 10 years.

Additionally, the officials said, federal authorities are investigating possible ties between traffickers and high-level state government officials.

"State officials seem very nervous, very tense," one official said. "We want to know why."

Chihuahua state Deputy Attorney General Oscar Valadez Reyes said the 13 police officers were not arrested but were detained for questioning by federal authorities. He said all the detained officers worked the night shift.

Asked about possible links between police officers and state government officials and the killings of women in Juárez, Mr. Valadez responded, "Among the different lines of investigations, none exist to support that theory."

Mr. Valadez said investigations into other officers were under way, but he stressed that "just because a handful of elements of one corporation are delinquents shouldn't smear the rest of the police force."

He said the state will "continue to collaborate" with the federal organized crime investigative unit and the attorney general "until the case is completely solved."

3 others arrested

Earlier, the owner of the home where the bodies were found and two members of his family were taken into custody as they tried to enter Texas, authorities said. Alejandro García Cárdenas was detained Tuesday along with his wife, Erika Mayorga, and their adult son, Alejandro García Mayorga.

Police said that Mr. García Cárdenas had confessed that he helped kill and bury at least a dozen people on the orders of a police commander and Humberto Santillán, who was arrested Jan. 15 in El Paso and is awaiting trial on U.S. charges of drug trafficking.

U.S. and Mexican officials have identified Mr. Santillán as one of the top lieutenants of the powerful Vicente Carrillo Fuentes drug cartel, which has controlled and terrorized this border region for more than a decade. Authorities said he had used the house where the bodies were found as a safe house.

The police officers' detention casts a spotlight on the law enforcement efforts of President Vicente Fox, who has pledged to address widespread crime and corruption by transforming Mexico into a country where the rule of law prevails.

State and local police in Ciudad Juárez and Chihuahua state have been accused repeatedly in recent years of having links to drug traffickers, interfering with the investigations into the women's deaths, and jailing innocent people in an effort to close cases.

7 victims identified

Since the weekend, the remains of 11 men have been exhumed from a yard behind a stucco house in a quiet Juárez neighborhood. Seven have been identified. Most had been strangled, police said. Some had been dead less than two weeks.

Police said Mr. García Cárdenas told them that more bodies were probably buried in the back yard – the same yard used to host neighbors for a recent dance to celebrate a baptism, according to neighbors. Things appeared so normal that last fall, they said, that the couple's 11-year-old son had asked a neighbor to watch over his dog because the family was going on vacation.

"This is so sick, sick, sick," said Patricia Garibay, an El Paso woman who had kept a vigil at the site awaiting news, possibly about her missing brother.

Ms. Garibay, who belongs to El Paso-based Association of Relatives and Friends of Disappeared Persons International, said her organization has compiled a list of at least 200 people who have been abducted and believed killed. At least 38 of the missing may be U.S. citizens, all believed victims of drug-related violence.

For Mr. Fox, reforming Mexico's judicial system is a top priority. Since taking office in 2000, Mr. Fox has repeatedly promised to change a culture of corruption throughout law enforcement that developed over seven decades of semi-authoritarian rule.

"Juárez is a big, big priority," said Mr. Fox's spokesman, Agustín Gutiérrez Canet. "The president is deeply committed. It's a defining issue."

Today, three years into his term, the Mexican legal system remains chaotic, say Chihuahua City human rights activists such as Sandra Medrano, who asserted that jails are packed with innocent people who lack the political connections or necessary cash to buy freedom.

"Money talks," said Ms. Medrano. "Laws are ignored."

Perhaps no other region represents a bigger test for Mr. Fox's promise of reform than Ciudad Juárez, where the killing of young women has been compared to a deadly sport.

Most are men

While the killings of young women have gained international attention, they are only part of the grim picture in Ciudad Juárez. Deputy Attorney General José Luís Santiago Vasconcelos, Mexico's chief prosecutor of organized crime, said that eight of every nine people killed in Juárez are men.

"This isn't just about women," Mr. Vasconcelos said in an interview. "It's about a breakdown in society. Everyone is a target."

Mr. Vasconcelos said the aim of the federal government is to "retake the border city of Juárez away from the drug lords. This is President Fox's way of saying enough is enough. We mean business. We want to clean up the mess. Right now, what you have are a bunch of criminals dressed as public servants."

Staff writer Ricardo Sandoval in Mexico City contributed to this report.