The Mexican drug cartels are notorious for the decapitated bodies they leave along the dusty highways south of the border, but they'd rather keep a low profile about another activity of theirs on U.S. soil -- horse racing, a sport in which involvement by mob figures has long been documented.

Now, the U.S. government has uncovered an extensive money-laundering operation by the drug cartel Los Zetas that involves buying and breeding racehorses in the States.

Federal agents raided a horse track in New Mexico and a ranch in Oklahoma Tuesday. Arrests were also made in Texas and California. Seven members of Los Zetas were arrested, while 14, in total, have been indicted in relation to the money laundering scheme.

This case highlights the capacity of Mexican drug gangs to establish footholds in legitimate U.S. industries and highlights the serious threat money laundering causes to our financial system, said Richard Weber, chief of the U.S. Internal Revenue Service's criminal investigation division.

Among those arrested was Jose Trevino, brother of a suspected Zetas boss Miguel Angel Trevino, who was among the 14 indicted but is believed to be in Mexico.

Trevino was arrested with his wife, Zulema, at their stables south of Oklahoma City. Together, they had run a front company called Tremor Enterprises, which used drug money to purchase and breed horses that were raced for substantial profit, generating $20 million according to the indictment.

This attack on the Zetas' most profitable money-laundering schemes is an essential front in the war on drugs and will financially disrupt this violent international criminal organization, Weber said.

Among some of their most successful horses were Mr. Piloto, winner of the $1 million All American Futurity at Ruidoso Downs racetrack in New Mexico, and Tempting Dash, which has earned nearly $700,000 in winnings. Other horses were given names referencing the illicit origins of their financial backing, such as Number One Cartel.

The stable manager at Southwest Stallion Station in Elgin, Texas, which houses Tempting Dash, declined to comment on his relationship with the Trevinos.

All I can tell you is that the horse is here, said Tyler Graham. I can't tell you anything else, because I don't know anything else.

The Zetas cartel, based in Nuevo Laredo, Mexico, directly across the Rio Grande from Laredo, Texas, is one of Mexico's most powerful criminal organizations, operating in the largest territory compared to any other cartel in the country.

The Zetas formed in 1999 from a group of deserters from the Mexican Army's special forces and are infamous for their brutal tactics, including decapitations, torture and the murdering of innocent civilians. They have also been known to employ local gangs in Texas to carry out assassinations across the border.