By Danna Harman Staff CIUDAD JUÁREZ, MEXICO The kingpins of this hemisphere's drug trade are no longer Colombians. In the largest reorganization since the 1980s, senior US officials say, Mexican cartels have leveraged the profits from their delivery routes to wrest control from the Colombian producers. The shift is also because of the success authorities have had in cracking down on Colombia's kingpins. As a result, Mexican drug lords are calling the shots in what the UN estimates is a $142 billion a year business in cocaine, heroin, marijuana, methamphetamine, and illicit drugs on US streets. "Today, the Mexicans have taken over and are running the organized crime, and getting the bulk of the money," says John Walters, the White House drug czar, in a phone interview. "The Colombians have pulled back." One consequence of the new dominance of Mexican cartels is a spike in violence, especially along the 2,000-mile US-Mexico border where rival cartels are warring not only against Mexican and US authorities, but also against one another for control of the lucrative transit corridors. While the Colombian cartels still control most of the production of cocaine and heroin, explains Jorge Chabat, a drug expert at the Center for Economic Research and Teaching (CIDE), a university in Mexico City, the more profitable part of the trade - transport to the US, and distribution there - has come under control of various Mexican cartels. Those organizations include: Osiel Cárdenas' Gulf cartel, Joaquín "El Chapo" Guzmán's Sinaloa cartel, Arellano Felix's organization in Tijuana, and the Juárez cartel, said to be led by Vicente Carrillo. "With the successful dismantling of some of the biggest cartels in Colombia, it was only natural that the Mexicans, who had for years had close contacts with the Colombians and knew the routes and the business, would take over," says Mr. Chabat. "...and now, they are fighting among themselves." The drugs, says Ron Brooks, president of the US National Narcotics Officers Association in West Covina, Calif., are either flown from Colombia to Mexico in small planes, or, in the case of marijuana and methamphetamine, are produced locally. Then, the drugs are shipped into the US by boat, private vehicles, or in commercial trucks crossing the border. US Border Patrol statistics show that last year 48 million pedestrians, 90 million private vehicles and 4.4 million trucks crossed from Mexico into the United States. According to the Bureau for International Narcotics and Law Enforcement Affairs, as much as 90 percent of the cocaine sold in the US in 2004 was smuggled through Mexican territory. Mexico is also the No. 2 supplier of heroin, the largest foreign source of marijuana, and the largest producer of methamphetamine. Moreover, Mexican criminal groups now dominate operations in the US, says the bureau's latest report, released in March, and control most of the 13 primary drug distribution centers in the US. US Consulate in Nuevo Laredo closed Nuevo Laredo, a town of 350,000 in the state of Tamaulipas, which sits across the Rio Grande from Laredo, Texas, has been hit hardest by the drug turf-war violence. Of some 820 registered drug-related killings in Mexico so far this year, 228 took place in the state of Tamaulipas, almost half of those in Nuevo Laredo, including two police chiefs and 21 police officers. Six journalists covering drug trafficking along the border have also been killed in the past 18 months.