A Mexican law enforcement official who worked with U.S. authorities was charged with sharing confidential information with drug traffickers and arranging the arrests of his drug boss' rivals, according to a far-reaching indictment against a gang that ferries drugs along California's border with Mexico.

Jesus Quinonez, the international liaison for the Baja California state attorney general's office, was among 43 defendants named in the federal racketeering complaint that alleges murder, kidnapping and other crimes. They are accused of working for Fernando Sanchez Arellano, who is widely considered the most-wanted drug kingpin in Tijuana, Mexico.

Quinonez and 30 others are in custody, while 12 defendants remained at-large, authorities said. Most of the arrests occurred Thursday and Friday — 27 in the San Diego area and four in Mexico.

Quinonez, 49, was arrested Thursday in San Diego during a traffic stop. He was a primary point of contact in Baja for U.S. law enforcement agencies and was a familiar figure at cross-border gatherings of government officials, including a Fourth of July party this month at the home of the U.S. consul general in Tijuana.

"We had a strong relationship with him, most of the (U.S.) agencies — federal, state and local," said Keith Slotter, special agent in charge of the FBI's San Diego office. "It was disturbing when he got caught up in this."

The indictment alleges that Quinonez shared "information" with a cartel associate in March about a triple homicide in Tijuana. Days later, the associate, Jose Alfredo Najera Gil, told another cartel operative that Quinonez was hoping the drug traffickers would buy him an apartment.

Quinonez appeared in court Friday in an orange jumpsuit with several other defendants, looking somber and turning his head occasionally to look at whomever was speaking. Magistrate Judge Ruben Brooks scheduled a hearing Aug. 3 to consider bail.

Patrick Hall, Quinonez's attorney, told reporters he couldn't comment on the charges because he had not read them. Quinonez did not respond to a message left on his cell phone by The Associated Press.

The Baja attorney general's office pledged to cooperate with U.S. authorities and said it would launch an internal investigation into Quinonez and another employee, Jose Antonio Ortega, who, according to the indictment, was "responsible for killing rival drug traffickers" and provided a photo roster of Baja police officers to a Sanchez associate.

Ortega was arrested Friday in Mexico, said Debra Hartman, a spokeswoman for the U.S. attorney's office in San Diego.

One U.S. law enforcement officer who worked closely with Quinonez said the Mexican official was Baja Attorney General Rommel Moreno's main envoy to U.S. authorities. He frequently visited San Diego.

"He was basically the face of the AG," said the official, who spoke on condition that he not be named because he was not authorized to speak publicly. "Whatever crimes they investigated and there was a nexus to the U.S., he was basically the go-to guy. It would be him or one of the agents below him."

The arrest comes at a time of growing cooperation between U.S. and Mexican authorities working to topple Mexican-based drug cartels whose primary market is the United States. Mexico's attorney general says at least 24,800 people have been killed in drug-gang violence since President Felipe Calderon launched his military-led offensive in 2006.

U.S. Attorney Laura Duffy said none of the information that Quinonez allegedly shared jeopardized anyone's safety. She, like other U.S. officials, insisted the arrest would not deter cooperation with Mexican officials. (Court documents identify the defendant as Quinones, but his business card and Mexican authorities indicate the correct spelling is Quinonez.)

Sanchez Arellano, also known as "El Ingeniero," or "The Engineer," is a nephew of the brothers who headed the Arellano Felix cartel, the Tijuana-based group that was once one of Mexico's top criminal organizations. Most of its leaders have been killed or jailed since 2002.

Sanchez's lieutenant, Armando Villareal Heredia, 32, was also named in the indictment, but U.S. authorities were unaware if Mexican officials had him in custody. He is listed on a Mexican attorney general's website of most-wanted fugitives. The indictment says he recently moved to the Guadalajara area.

Sanchez was not named in the indictment and officials declined to say if he was facing any charges under seal.

Duffy said the arrests were a "significant hit" to Sanchez's organization.

"They're on their knees today, trying to recover from what happened," she said at a news conference.

Federal officials began investigating the defendants in January after an initial investigation by the San Diego district attorney's office.

Authorities seized a ton of marijuana, 30 pounds of meth and 15 pounds of cocaine during the investigation, Duffy said.

The indictment opens a window into the Mexican organization's apparent reach in the United States. Nearly half of those charged live in Southern California, many in the San Diego area.

A 20-year-old from the upscale suburb of Poway allegedly attempted to rob and kill and carjacked a 2008 Ford Explorer. A 23-year-old from Chula Vista is accused of attempting to murder Sanchez's rivals in San Diego.