(NewsNation) — Rival factions of the Sinaloa drug cartel are waging a deadly war in northwestern Mexico, leaving dozens dead and missing in the wake of U.S. arrests of key cartel leaders.

The violence between groups known as the “Mayos” and the “Chapos” erupted after U.S. authorities apprehended Joaquín Guzmán López and Ismael “El Mayo” Zambada in late July.

Mexican President Andrés Manuel López Obrador claims these arrests, which he says were made without Mexico’s knowledge, triggered the current bloodshed.

“They made a deal and did not inform us,” López Obrador said, citing Mexico’s attorney general. “The Department of Justice was in talks with one of the criminal groups in Sinaloa and they made deals.”

More than 50 people have been killed and another 50 are missing in Culiacán, the capital of Sinaloa state. Gruesome displays of violence include severed heads left on pizza boxes and bodies wearing baseball caps similar to those in “El Mayo” wanted posters.

The conflict has disrupted daily life in Sinaloa. While schools have reopened, many businesses close early and residents remain indoors despite heavy military patrols.

U.S. intelligence analysts suggest the conflict could last for years. The Drug Enforcement Administration reports the Sinaloa and Jalisco cartels have a presence in all 50 U.S. states, controlling global networks that dominate the fentanyl and methamphetamine trade.

López Obrador questioned why the U.S. hasn’t focused on arresting its own drug lords and blamed America’s demand for driving the surge in fentanyl trafficking.

U.S. officials have not yet responded to these accusations.

The Mexican president’s claims have sparked debate about U.S.-Mexico cooperation in combating drug cartels.