U.S. federal agents have rounded up more than 750 suspects in a wide-ranging crackdown on Mexican drug cartels operating inside the United States.

More than 50 of the suspects were arrested overnight in a series of raids coordinated by the Drug Enforcement Administration. The operation is aimed at capturing members of the Sinaloa cartel, blamed for a rising tide of violence in Mexico and the United States.

And it's that rising violence coupled with drug-related crimes that represent a very serious security challenge to the United States, says a homeland security expert at Texas A&M University.

Dave McIntyre, who heads the Integrative Center for Homeland Security at the university, is an expert on security and terrorism matters, and explains that Mexican drug cartels have established networks in almost every major U.S. city.

“They fight among themselves for the trade routes into the U.S.,” McIntyre says. “In recent years, the Mexican government has tightened down on the leadership of drug gangs, but the result has been that the violence has increased dramatically.”

He notes that the drug cartels are ruthless – they kill to make a point and to strike fear into anyone that presents a threat to them.

“They not only kill policemen, they kill their entire families, including children,” he adds, noting that the police chief of Cancun recently came out of military retirement and was killed within a week.

“They are lawless and they make their own rules. And they also are extremely well-armed. Many times, the drug gangs have superior firepower over local police. The sophistication of their weapons has greatly increased, such as using anti-tank weapons and .50 sniper rifles as well as foreign-made grenades. You didn’t see those types of weapons in the past, but now they are common."

One U.S. agency report estimates that at least 1,000 guns are smuggled into Mexico every day, most of them winding up in the hands of the drug gangs.

Ironically, according to a joint Houston Chronicle, San Antonio Express News investigation, most of the guns smuggled into Mexico come from the United States.