NEW YORK -- A pair of huge drug busts that led to the seizure of 270 pounds of drugs, including 141 pounds of pure fentanyl, were made after key transactions were witnessed by investigators in parking lots of a Walmart and Home Depot in New Jersey, authorities said.

The first -- the largest fetanyl bust in New York City history -- occurred Aug. 1 and involved a shipment that two alleged traffickers picked up outside a Walmart in the Manahwakin section of Stafford, according to authorities.

The second bust occurred Sept. 5 after New York narcotics officers and members of the New Jersey Drug Enforcement Association watched two Bronx men pick up a duffel bag from a tractor-trailer in a rear parking lot of the Home Depot on Route 9 in Woodbridge, according to authorities.

The total take from the busts was 270 pounds of drugs with an estimate street value of $30 million. Four New York residents face multiple charges, the New York Office of the Special Narcotics Prosecutor said in a statement Monday.

In the arrests linked to the Walmart drop in Ocean County, Rogelio Alvarado-Robles, 55 and Blanca Flores-Solis, 51, both of Queens, N.Y., picked up a shopping bag authorities said contained drugs from an unidentified man as they were being watched by detectives from the New Jersey Drug Enforcement Administration.

The pair then got back into a silver Mercedes with Florida license plates and returned to their apartment in the Kew Gardens section of Queens. Cops seized the shopping bag, which had been placed in a backpack and contained more than two pounds of cocaine, according to the prosecutor.

Police then obtained a search warrant and found four suitcases and a purse inside one of the bedrooms in the apartment. The suitcases and purse contained 97 packages of drugs, 86 of which included fentanyl, authorities said.

The packages had more than 141 pounds of pure fentanyl and more than 48 pounds of fentanyl mixed with heroin, the synthetic opioid tramadol and the tranquilizer ketamine.

The pure fentanyl seized could have produced about 32 million lethal does, officials said.

Alvarado-Robles and Flores-Solis were each charged with two counts of first-degree criminal possession of a controlled substance and two third-degree counts of the same offense.

In the arrests from the Home Depot parking lot exchange, Edwin Guzman, 35, and Manuuel Rivera-Santana, 32, retrieved the drugs from the tractor trailer and left in a Toyota Sienna.

Detectives and agents pulled them over near the 161st Street exit on the Major Deegan Expressway, not long after they crossed the George Washington Bridge.

Officers got a search warrant and found the duffel bag, which they said contained 25 brick kilogram-size packages. Each had pure fentanyl or a fentanyl/heroin mixture.

Guzman and Rivera were each charged with one count of conspiracy and two counts criminal possession of a controlled substance.

Jeff Goldman may be reached at jeff_goldman@njadvancemedia.com. Follow him on Twitter @JeffSGoldman. Find NJ.com on Facebook.