A major Colorado drug-smuggling operation that posed as a legal provider of medical marijuana sometimes used sky-diving planes to carry the pot to Minnesota, according to authorities in Denver.

Several Minnesotans, either still living here or recent arrivals in Colorado, are accused of playing significant roles in the 32-person, multimillion-dollar enterprise. Minnesota's prominence in the pot pipeline was reflected in the name authorities gave to the sting — "Operation Golden Gofer.''

"This investigation shut down one of the largest and most sophisticated criminal enterprises uncovered since Colorado voters passed Amendment 20 [legalizing medical marijuana] in 2000," said Colorado Attorney General Cynthia H. Coffman. "Illegal drug dealers are simply hiding in plain sight, attempting to use the legalized market as a cover."

The pot ring posed as a medical marijuana caregiver in Colorado ­— where medicinal and recreational use of the drug is legal — as they trafficked in tens of thousands of pounds of the substance, sending large shipments to Minnesota, Coffman's office said.

After the planes landed and delivered the pot, they flew cash payments back to Colorado, according to investigators.

Charged with leading the multistate operation was Coloradan Tri Trong Nguyen, 39.

"At one point, Nguyen explored becoming a legitimate grower by merging his operations with a licensed dispensary," Coffman said. "But when Nguyen was told he would have to cut down his existing marijuana crop and start the business again in accordance with Colorado law, he responded that he was making too much money doing what he was doing and he walked away from the deal — choosing the more lucrative black market over the white market."

Joseph Johnson, a conspirator based in Winsted, Minn., confessed to being a"gofer" for the operation by using his sky-diving business and a vehicle to transport hundreds of pounds of marijuana from Boulder to Minnesota aboard his planes.

Last June, Johnson was intercepted in Kansas with about 60 pounds of pot in his vehicle and $330,000 in cash, authorities said. He agreed to help the DEA gather evidence against his co-conspirators to reduce his punishment.

The primary shipment recipient in Minnesota was Thomas "C.T." Dispanet of Minneapolis, according to investigators. Dispanet, 40, "was one … a few trusted individuals on the receiving end of hundreds of pounds of the … Colorado grown marijuana," the indictment read.

Dispanet received the shipments, delivered by car, truck or plane, and sent the marijuana to lower-level dealers in Minnesota, investigators allege.

Dispanet would typically receive up to 400 pounds of marijuana a month, collect cash payments from transactions in Minnesota and send the money back to his Colorado cohorts, according to the indictment.

At the time of his indictment, Dispanet was living alone in a two-story home in the 1700 block of Irving Avenue N. Sheets covered all of the windows and no one answered the door Thursday evening.

A neighbor, who asked not to be named, described Dispanet as a private person who was rarely seen outside his house. No one knew what Dispanet did for a living, the neighbor said.

Dispanet owned a number of lowboy and horse trailers that he would frequently power-wash in the alley behind his house. On Oct. 28, the neighbor watched police conduct a two-hour search and seizure of Dispanet's home and truck, but doesn't know what was taken.

In the nine years the neighbor has lived on the block, the windows have been completely covered at the home where Dispanet lived.

Friend joined operation

A longtime friend of Dispanet's, 37-year-old Patrick Concannon, is accused of leaving the Duluth area two years ago to work as a grower for the operation. Investigators say Concannon helped cultivate and package hundreds of pounds of marijuana for shipment.

Accused of assisting Nguyen are two of his sisters: Oanh "Liz" Tran, 48, a former nurse in Minnesota who allegedly helped grow the plants in Colorado and launder illegal proceeds from sales, and Anh Thi "Lana" Nguyen, 37, who left Minnesota in recent months and is accused of growing marijuana and laundering money.

Also indicted was 39-year-old Cuyler Gerbich, described as a high-level conspirator who moved from St. Paul to Colorado in 2009 to help set up the growing operation and act as the primary transport coordinator.

According to authorities in Colorado:

Nguyen headed the multistate operation with the support of his wife, three sisters and dozens of co-conspirators. For four years, Nguyen and the others presented themselves as caregivers to medical marijuana patients, as property managers servicing marijuana growers, as marijuana "cooperatives" and as small-business owners while they trafficked tens of thousands of pounds of marijuana, concentrate and butane hashish oil out of state.

A tip in January 2014 led Denver police to an unlicensed marijuana growing warehouse. The operator, Michael Glick, claimed the "co-op" was legally growing plants for five medical marijuana patients.

The probe led to the seizure five months ago of 4,600 pounds of marijuana, nearly 2,000 marijuana plants, 10 pounds of hashish oil and $1.4 million in cash.

Nguyen controlled the illegal cultivation and distribution of marijuana at 13 Denver warehouses. The organization allegedly laundered the proceeds, avoiding taxes. They disguised their operation through front companies that included a massage parlor and a purported property-management company leasing commercial warehouse space to marijuana growers.

The family converted cash from illegal sales into money orders that they then deposited into bank accounts in amounts under $3,000 to avoid triggering federal reporting requirements. They also avoided payment of an estimated $700,000 in excise taxes.

The defendants collectively are charged with 52 felony counts, and most are under arrest awaiting trial dates in Denver District Court.

Paul Walsh • 612-673-4482

Liz Sawyer • 612-673-4648