LYNN – Law enforcement officials concluded a two-year drug investigation at a Lynnway parking lot Saturday when police confiscated a tractor-trailer truck carrying 185 pounds of cocaine worth $8.4 million ? marking Lynn’s largest drug bust in the last several years.Six people were arrested and will be arraigned today in Lynn District Court.The Essex County District Attorney’s Office said police set up surveillance about 2 p.m. and observed a flatbed tractor-trailer unit pull into the Lynnway parking lot. At that time, some of the suspects offloaded most of the total 84 kilos of cocaine into suitcase-like containers and placed them into a pickup truck, authorities said.Those two vehicles, along with one other car involved in the operation, then left the parking lot but were quickly stopped by police, according to Essex DA spokesman Steve O’Connell. All six occupants were arrested without incident, he said.O’Connell declined to provide the exact location of the drug bust.Each of the suspects was charged with one count of trafficking over 200 grams of cocaine and one count of conspiracy to violate narcotics laws.The suspects are from different parts of the United States and Mexico. Authorities declined to provide specifics about how the suspects are connected or what kind of operation they might have conducted.The suspects are identified as: Rafael Mercedes, 44, of 6 Glines Ave., Roxbury, Sergio Valderinos, 42, of 21 Blue Hill Ave., Boston, Modesto Castillo, 41, of Chicago, Adam Alcala, 40, of Benton, Ark., Raul H. Cortinas, 37, of Mission, Texas and Guille Garcia, 32, of Francisco, Mexico.If convicted of trafficking over 200 grams of cocaine, the defendants face up to 20 years in state prison, with a minimum mandatory sentence of 15 years.The arrests and drug seizure came as the result of a two-year investigation spearheaded by the Essex County Drug Task Force assigned to the Office of Essex District Attorney Jonathan W. Blodgett. Lynn Police and the federal Drug Enforcement Agency assisted in the investigation. Also taking part in Saturday’s arrests were State Police assigned to the Revere Barracks and members of the State Police Canine Unit.