Federal prosecutors have indicted 75 people including 40 in San Diego in a massive drugs and money operation which has been called the biggest money laundering investigation ever in the Californian city.

The defendants allegedly laundered drug proceeds from the Sinaloa cartel for years, U.S. Attorney Adam Braverman said at a news conference in downtown San Diego.

He said the network was responsible for laundering tens of millions of dollars in drug profits over the past three years.

Law enforcement seized more than $6 million in cash. Authorities charged 40 people in San Diego on Thursday with conspiring to launder tens of millions of dollars in drug money

209 pounds of methamphetamine, 138 pounds of heroin, 22 pounds of fentanyl, 202 pounds of cocaine and 554 pounds of marijuana worth millions of dollars on the streets were seized

20 firearms, including semiautomatic rifles and handguns (pictured) were also seized

'We have siphoned the cash and life out of a San Diego-based international money laundering organization with ties to the Sinaloa cartel,' Braverman said.

According to the San Diego Tribune, investigators managed to seize $6 million in cash thanks to a three-year probe undertaken by the FBI's Cross Border Violence Task Force.

Hundreds of pounds of drugs like methamphetamine, fentanyl, heroin, cocaine and marijuana were also seized.

Roberto Lopez-Albarran, 32, the alleged leader of the operation was arrested in San Diego on February 9 and had already been in custody for the last month.

'We have siphoned the cash and the life out of a San Diego-based international money laundering organization with ties to the Sinaloa Cartel,' U.S. Attorney Adam Braverman said

Authorities discovered large quantities of fentanyl, heroin and methamphetamine

Another 35 people were charged in other parts of the country, said U.S. Attorney Adam Braverman, pictured, at a press conference

Another 21 people who were named in a series of four other related indictments that were handed down by a San Diego grand jury are also in custody.

Although the investigation focused on activity in San Diego, 35 others were charged for their role in money laundering and drug sales in federal courts in Ohio, Kentucky, Kansas and Washington.

25 of those defendants were in custody as of Thursday.

As leader of the organization, Lopez allegedly oversaw a large network of people dubbed 'money movers' who moved huge amounts of cash around the country which was then taken back to Mexico.

The cash would be hidden in secret compartments of vehicles, or in cash-stuffed duffel bags, luggage and even shoe boxes.

The money would be deposited into banks in quantities under $10,000 to avoid regulators

The FBI deployed undercover agents and task force officers from various law enforcement to infiltrate Lopez-Albarran's organization and help bring cash across the border

They picked up the cash in parking lots, hotels and restaurants in San Diego and other cities large including Dayton, Ohio, Los Angeles, and Lexington, Kentucky.

The cash was then deposited into banks using so-called 'funnel accounts.'

The accounts were set up to receive deposits from multiple states but were deposited in chunks of less than $10,000 to avoid having to file additional paperwork with regulators.

Once in the American banks, the money would be wire transferred to Mexico and into bank accounts for bogus Mexican companies.

Manuel Reynoso Garcia, 62, is accused of orchestrating the money-laundering activities.

The 62-year-old Garcia was charged last month in federal court with money laundering conspiracy and other charges. He has pleaded not guilty and has been released on a $25,000 bond.

The investigation ended up using undercover work by investigators from the San Diego District Attorney's office and Chula Vista police who were able to infiltrate the organization.

The group even used code words as well as WhatsApp, to communicate about the money movements and transfers.