A Dorchester man and two alleged accomplices are scheduled to answer fentanyl and meth charges in federal court on Monday, as part of what could be a larger national investigation that started two years ago.

Jeffry Carmona, also known as "El Gordo" ("Fats" in English), Miguel Polanco and a woman, known, at least as of a week ago, only as Natacha, are due to appear in US District Court Monday afternoon on charges of distribution of 400 or more grams of fentanyl, distribution of 100 grams or more of fentanyl analog and distribution of 500 grams or more of methamphetamine, according to court documents unsealed on Friday.

An affidavit by an FBI agent on the case describes an investigation that began in January, 2020 into a growing nexus between drug suppliers and Bitcoin money launderers. Agents trained in the use of the online-based cryptocurrency began posing as drug buyers and "picked up bulk cash believed to be drug proceeds from various money launderers and drug traffickers in multiple locations around the United States and transmitted Bitcoin to wallets identified by the traffickers."

In the Boston area, agents convinced a man facing more general money-laundering charges to work with them, which helped lead them to a money-laundering drug supplier in Culiacan, the capital of the Mexican state of Sinaloa. That man, convinced the agents were themselves money launderers and drug dealers after they helped him launder $100,000 via Bitcoin, connected them to Carmona, to whom he was allegedly shipping fentanyl in both powder and pill form, methamphetamine and cocaine. According to the affidavit:

"On April 27, 2021, after coordinating with a suspected money launderer, an agent acting in an undercover capacity ('UC-1'), conducted a pickup in Boston of $100,000 of suspected drug proceeds to be laundered through a Bitcoin transfer. The money courier traveled from New York to Boston with the bulk cash. UC-1 collected the cash from the courier, and another agent acting in an undercover capacity ('UC-2') transmitted $100,000 of Bitcoin to a wallet identified by the suspected money launderer. Shortly after this April 27, 2021 transaction, UC-1 received a text message from a Mexican phone number, 52-667-207-5815. The user of that phone number identified himself as being from Culiacan, Mexico (hereinafter, 'CO-CONSPIRATOR 1'). CO- CONSPIRATOR 1 stated that he had received many of the Bitcoin transfers that UC-1 had conducted in the Boston area. Since that first April 27, 2021 introduction, CO-CONSPIRATOR 1 and UC-1 have continued to communicate and have arranged multiple bulk cash drop-offs in exchange for Bitcoin in locations throughout the U.S. "

Over the coming months, in fact, continuing until at least early this month, the affidavit continues, agents made a number of drug purchases and pickups from Carmona, including various quantities of fentanyl and meth. Agents would pay Carmona four-figure fees for his trouble, then, after receiving the drugs - typically a few grams short of what they had been promised - they'd transfer tens of thousands of dollars to El Patron's Bitcoin "wallet."

Carmona told the undercover agents he was the "right-hand man" for the supplier the agents knew as "Co-Conspirator 1" but whom Carmona referred to via the honorrific of "El Patron."

Many of the transactions were done outside an apartment building at Blue Hill Avenue and Seaver Street, about two miles from Carmona's apartment on the third floor of a three decker on Burt Street, off Washington Street, where agents say he stored drugs.

Unusual for a drug dealer, however, Carmona did not drive a fancy car, or any car there: He would take a T bus. In fact, he told one of the undercover agents, he prefers public transportation, even for transporting drugs to a sale.

The affidavit recounts agents watching Carmona, in part through a camera slipped on a pole outside his three decker, walking a few blocks to get on a bus up to Blue Hill Avenue. The affidavit does not specify which bus, but the 22 route from Ashmont, which is a few blocks from his apartment, has a stop at Blue Hill Avenue and Seaver Street.

After one deal on Blue Hill Avenue, the affidavit continues, agents watched Carmona walk all the way back home to Burt Street; another time, though, he did take a taxi to a drug sale.

And once, to discuss further sales, and just to relax for a night, he hopped into a car driven by an accomplice of the undercover agent for a ride up to the Encore Casino in Everett.

Over the course of the investigation, agents purchased everything from a five-kilo load of meth on July 20, 2021, for which they paid Carmona $1,000 in cash and El Patron $34,000 via bitcoin, to three kilos of fentanyl on Nov. 7, 2021, for which an agent put $70,000 worth of Bitcoin in the Mexican man's online "wallet."

The last recorded purchase was of fentanyl pressed into 2,000 pills, about 250 grams in total, for which one of the agent's "cooperating witnesses" handed $6,000 to Camona. Carmona, the affidavit says, expressed disappointment he was only getting $6,000, but the undercover buyer said that was all his "boss" had given him.