Federal agents Tuesday announced the largest heroin bust they've ever had in New York State and the fourth-largest in the United States, with authorities seizing at least $50 million worth of the drug believed tied to Mexico's powerful Sinaloa Cartel.

Authorities said some of the heroin was likely earmarked for lower-level dealers in Nassau and Suffolk.

More than 175 pounds of heroin were discovered Sunday in a secret compartment under the floorboard of a sport-utility vehicle and inside a wall in a Bronx apartment, authorities said.

During the raid, officials said, agents also seized more than $2 million in cash hidden under the floor of another Bronx apartment near the exclusive Fieldston neighborhood.

"This load was so large it carried the potential of supplying a dose of heroin to every man, woman and child in New York City," said Bridget Brennan, New York City's special narcotics prosecutor. "While this important seizure stopped a huge amount of heroin from flooding our city, it also highlights the critical need to intercept heroin before it ever reaches our region."

From left, Jose A. Mercedes, also known as "Hippie," and Yenci Cruz were arrested by federal agents who seized the fourth largest heroin bust in U.S. history and the largest in New York history on Sunday May 17, 2015. Photo Credit: DEA

The Bronx-based syndicate received monthly heroin shipments from Sinaloa suppliers in Culiacan, Mexico, where the cartel is based, authorities said.

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Most of the heroin currently sold on Long Island and across the five boroughs is smuggled into the United States by Sinaloa, considered the world's largest drug-trafficking organization, officials said.

The seizure followed a yearlong investigation by Brennan's office and the DEA's New York Drug Enforcement Task Force, made up of DEA agents, NYPD detectives, State Police investigators and a homeland security task force.

The probe culminated Sunday with the arrests of the alleged head of the Bronx syndicate, Jose A. Mercedes, also known as "Hippie," and an alleged member, Yenci Cruz Francisco, officials said. The Bronx men are charged with operating as a major trafficker and possession of a controlled substance.

Two other alleged members of the organization -- Mercedes' son, Jose Mercedes Jr., and Juan Infante -- were arrested in November as part of the same investigation, officials said.

In the days leading up to Sunday's raid, authorities intercepted phone conversations suggesting the organization was expecting delivery of a large load of heroin over the weekend. Agents set up surveillance outside an address in the 200 block of West 251st Street, near Fieldston, where the organization was suspected of maintaining a stash apartment, officials said.

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They followed several vehicles to New Jersey, then back to the Bronx, where they found an unspecified amount of heroin in a hidden compartment in Mercedes Sr.'s Kia Sorento, officials said.

A secret compartment under the floor was found in Cruz's Chevy Suburban, officials said. Inside, agents found 70 kilograms of heroin -- 154 pounds -- and $24,000 in cash.

Agents also searched several Bronx apartments associated with the group. Inside Apt 1D at 2851 Webb Ave., agents found 10 kilograms (22 pounds) inside a wall; inside Apt. 5E at 210 W. 251st St., agents found the $2 million under the floor, officials said.

Mercedes Sr. and Francisco were arraigned in criminal court in Manhattan and ordered held without bail.

"We are fully investigating the case to determine the proper course of action," said attorney Patrick Brackley of Manhattan, who is representing Mercedes Sr.

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Prosecutors charged Mercedes Jr. and Infante with possession of a controlled substance and drug paraphernalia charges. Arraignment information was not available. Their lawyers could not be reached.