A massive international drug and money-laundering bust resulted in the seizure of 273 pounds of heroin with a street value of $40 million, Colorado and federal agents and prosecutors announced Wednesday.

“Heroin use in Colorado has reached epidemic proportions,” said state Attorney General Cynthia Coffman. “This bust deals a knockout punch to a highly organized and invasive bunch of traffickers.”

Dubbed “Operation Chump Change,” the two-year investigation was described as “the most complex heroin bust in the history of the Rocky Mountain region,” resulting in dozens of federal and state indictments.

Agents with the U.S. Drug Enforcement Administration began tracking a money-laundering operation in 2013, and the investigation led agents to a drug cartel that grew opium poppies and operated heroin laboratories in Mexico, as well as smuggled drugs into the western U.S.

Brown heroin was smuggled into Colorado in large quantities and sold on the 16th Street Mall and in City Park in Denver, said Rob Saccone, a DEA strike-force agent. Brown heroin, which can be smoked or snorted, was sold relatively cheap, in $10 and $20 packets.

The alleged leaders of the cartel — a man and his son in Mexico — have been identified but not yet arrested, said U.S. Attorney John Walsh. He expects they’ll be tracked down, arrested and extradited to Colorado to face multiple charges.

The investigation led to 54 state-level indictments and three federal indictments charging 34 suspects “with complex money laundering and violations of the drug king-pin statute,” officials said.

On May 14, 15 search warrants were served on suspected heroin traffickers across Colorado and 24 suspects were arrested. Additional search warrants were served and arrests made in Arizona, Nevada, Utah and California.

The coordinated effort illustrates that law enforcement and judicial officials “will not sit back and let hard drugs overtake our state,” Coffman said.

“This case,” Walsh added, “represents the gold standard for federal-state law enforcement cooperation to attack and dismantle a dangerous international narco-trafficking organization.”

Officials called the investigation “Operation Chump Change” because some early seizures and arrests, involving amounts in the $100,000 range, seemingly failed to slow the operation.

The operation also netted:

• 31 pounds of methamphetamine, valued at $500,000.

• 25 pounds of cocaine, valued at $1 million.

• 25 vehicles, worth about $300,000.

• $2.3 million cash.

Kieran Nicholson: 303-954-1822, knicholson@ denverpost.com or twitter.com/kierannicholson