KEY POINTS:
Mexican drug cartels are shipping more than huge quantities of drugs north of the border.
Increasingly, they also are exporting bloody mayhem.
Seeking to stem the growing influence of Mexico's Sinaloa cartel, federal agents arrested more than 50 suspects in raids at different ends of the country.
The raids capped a 21-month operation by the Drug Enforcement Administration that rounded up 755 suspects and seized more than US$59 million in criminal proceeds.
