State authorities said that the 12 alleged gunmen killed by Mexican armed forces on July 10 and 11 in the Sinaloan cities of Guasave and Sinaloa de Leyva worked for Meza Flores, as Proceso and other outlets reported. Among the dead were Chapo Isidro's chief of security and two other men with outstanding warrants. Mexican authorities also carried out a series of arrests in the region and seized weapons and vehicles.

The group headed by Meza Flores is often called the Mazatlecos, though it is given other labels as well. Whatever its name, the group has carved out a stranglehold in Guasave and other areas in Sinaloa, especially in the northern portion of the state. Sinaloa officials said that detaining Chapo Isidro (also sometimes called Chapito Isidro) is now a primary objective of federal and state officials, who are working in tandem. State officials have said that the search for Chapo Isidro will concentrate on the northern Sinaloa region where he is based:

"[Meza Flores] is being searched for and we will also seek at the same time to continue investigating other people that we have located in that area, to see if it is possible to detain them … Yes it is people from that area, we are working in coordination with the armed forces there."

The search for Meza Flores is not an entirely new development: previous reports have indicated that the army has executed operations to arrest him on three occasions, and has failed each time.

InSight Crime Analysis

Meza Flores' profile has rocketed in recent years, first as a rival to Sinaloa Cartel boss Joaquin "El Chapo" Guzman, and now, since Guzman's detention, as a potential replacement for the region's most prominent trafficking boss.

Meza Flores is thought to be 32 years old, and was an anonymous Sinaloa operator in 2008 when he sided with the Beltran Leyva Organization (BLO) after it split with the Sinaloa Cartel. In the years thereafter, Meza Flores and his group became the most important Sinaloa-based allies of the BLO, allowing Hector Beltran Leyva to retain ties to his home state despite moving much of his organization south. Thanks in large part to the growth of the Mazatlecos in Guasave, Sinaloa Cartel rivals -- including the BLO, the Zetas, and the Juarez Cartel -- had a base from which to harass Guzman's forces. 

Meza Flores' group has retained its hold over much of northern Sinaloa despite persistent attempts by rivals in the Sinaloa Cartel to drive them out. Dating back to 2011, banners have appeared in Guasave, Meza Flores' hometown and the geographic center of his operation, taunting Joaquin "El Chapo" Guzman for his inability to make inroads in the town. In the years since, similar reports regularly emerged of Chapo Isidro and his allies resisting Guzman and company in northern Sinaloa cities. 

The organization's profile spiked further in January 2013, when the US Treasury Department designated Meza Flores' gang a drug trafficking organization under the so-called Kingpin Act, giving the government added power to seize assets belonging to Meza Flores. The US accused Meza Flores of trafficking heroin, cocaine, and marijuana into the US, and also named a handful of businesses used as fronts by the Mazatlecos. 

Since then, Meza Flores has been among the most prominent of the younger generation of Mexican traffickers.

As the Mexican underworld evolves in the post-Chapo Guzman era, Meza Flores' group has some substantial built-in advantages. His base in northern Sinaloa stretches from Guasave, just a few miles from the coast, to the Golden Triangle, the mountainous region where many of the nation's marijuana crops are produced, and which borders Chihuahua on the other side. Meza Flores is also younger than his rivals in the Sinaloa Cartel, whose current leader, Ismael Zambada, is in his 60s. And Meza Flores has had the good fortune to have grown in stature during a period in which the Sinaloa Cartel leadership has been devastated. As a result, the most potent and obvious counterweight to his group could be tottering.  

Of course this is largely, if not entirely, dependent on Meza Flores staying out of prison. The public declaration of government interest in Meza Flores in both the US and Mexico does not bode well for his survival. Unlike Guzman, for instance, who was rumored to have traveled around Latin America as he stayed a step ahead of the police for more than a decade, Meza Flores does not appear to have a far-flung network to fall back on.

However, there is no public groundswell demanding his arrest, making it far more likely that government interest will eventually wane. And, as seen in the long hunt for Chapo Guzman, declaring a target to be a priority is a very different matter than actually bringing them into custody.