Police in El Cajon said they arrested more than 60 people who are suspected of being affiliated with the Chaldean Organized Crime Syndicate based in Detroit.
Smugglers were shipping drugs provided by the Sinaloa Drug Cartel from El Cajon to Iraqis in Detroit, authorities said.
El Cajon police and federal agents say they have seized 18 pounds of methamphetamine, narcotics, cocaine and other drugs; more than 3,500 pounds of marijuana; $630,000 in cash; four Improvised Explosive Devices (IEDs); and more than 30 guns, including assault rifles.
Steve Tomaski, assistant special agent in charge for the Drug Enforcement Administration's (DEA) San Diego office, described the IEDs as "small pipe bombs". He did not explain what the explosives may be used for and said the FBI is handling that part of the investigation.
A social club in El Cajon played a key role in the alleged criminal operations.
"That was somewhat of a hub for criminal activity, primarily gambling and things of that nature," Tomaski said. "It was also a safe haven for any criminal element pretty much to go in there and discuss criminal activity and conspire and plan for future crminal activity."
In April, a DEA undercover agent was shown a hand grenade by an immigrant and was told additional grenades were available from a Mexican military source.
The cartel linked with the Chaldeans - Sinaloa - is Mexico's most powerful drug cartel, led by Joaquin "El Chapo" Guzman, who has become one of the world's richest and most-wanted men since he escaped from a Mexican prison 10 years ago. William Sherman, acting special agent in charge of the DEA's San Diego field division, said the Sinaloa cartel was supplying the drugs to the ring and the investigation resulted in the seizure of 3,500 pounds of marijuana from the cartel. The Iraqis were believed to be planning to distribute a portion of that load, Sherman said.
Officials said they believe the firearms and explosives were destined for the local market.
About half of the 60 arrested face federal charges and half face state charges. Officials said the investigation is ongoing and there could be more arrests.
Detroit and San Diego have the largest and second-largest populations of Chaldeans in the United States. Chaldeans are descendants of the ancient inhabitants of Mesopotamia - what is now Iraq - and many have fled to escape persecution for their Christianity.
Officials say the Chaldean syndicate has a longstanding relationship with the Sinaloa cartel. Many Chaldeans passed through Tijuana on their way to the United States, helped by Mexican migrant smugglers, authorities said.
El Cajon police have for years received complaints from neighbors and the wives of men who attended the club. The managers of the club are aware of the criminal activity and demand a cut of the money, according to authorities. Armed guards are allegedly provided during high-states card games.
The club's troubles go back more than a decade. In 1998, police seized illegal slot machines. In 2007, it was identified as a gathering spot for Iraqi narcotics distributors. In 2009, authorities started investigating the illegal sale of firearms and possession of hand grenades.
Four indictments were unsealed Thursday charging nine people with federal narcotics and weapons trafficking charges and the unlawful possession of various firearms and explosives. One of the suspects, Nofel Noel Suleyman, was also charged with engaging in a continuing criminal enterprise, which carries a mandatory minimum sentence of 20 years in prison.
The Associated Press contributed to this report.