Mexican federal army troops have taken control of the border city of Nuevo Laredo, and detained 41 local police for questioning. The crackdown comes after local police opened fire on federal agents sent in to investigate the murder of the newly-appointed police chief. A surge of drug-related violence in the city has claimed 45 lives this year.

Mexican President Vicente Fox launched "the mother of all battles" on the drug trade, sending hundreds of armed police to the border cities in March to restore order. But concerns about lawlessness were reignited last week with the killing of Nuevo Laredo's police chief, Alejandro Dominguez, a day after he took office.

On June 11, federal agents sent in to investigate the killing got into a shoot-out with municipal police. President Fox's government accused local police of being in the pay of drug traffickers. "There are very clear signs of a relationship between elements of the Nuevo Laredo police and drug smuggling, hence the decisive action," said government spokesman Ruben Aguilar.

Troops in Humvee all-terrain vehicles patrolled the city's streets and elite forces stood guard on street corners. The detained officers were taken to Mexico City for questioning about the shoot-out, in which one federal agent was wounded. Nuevo Laredo officials said local forces may have thought the federal agents were members of a drug gang posing as police officers. (BBC, June 14)

The violence appears to be a struggle between Mexico's three top drug cartels. The leadership of the Tijuana and Gulf cartels are largely behind bars, but have formed an alliance behind bars to fight Joaquín "El Chapo" Guzmán, who is attempting to appropriate their turf for his own Juarez cartel. Nuevo Laredo, along the Rio Grande between Juarez and Matamoros, has traditionally been undercontrol of the Gulf cartel. Guzmán, believed to be hiding in remote mountains, protected by the local population, has eluded capture, and is increasingly compared to the legendary Colombian kingpin Pablo Escobar. (El Universal, May 31)

See our last post on the growing violence in northern Mexico.