To the employees at the Conifer post office, something about the outgoing package smelled funny.

The way the label was filled out seemed off. The addresses were funky. And then there was the odor emanating from it: The package reeked of marijuana.

A police drug-sniffing dog confirmed the suspicions on two incoming packages addressed to the return address on the outgoing parcel. By the time U.S. postal inspectors knocked on Ian Mair’s door last summer — after simply studying the outside of his mail — they had enough information to persuade Mair to show them his marijuana-growing operation, according to an asset-forfeiture filing in federal court. Mair is scheduled to be arraigned next month in Jefferson County Court on charges of marijuana cultivation and possession.

These are busy times for postal inspectors in Colorado.

Investigators at the U.S. Postal Inspection Service in the state said that, anecdotally, they have seen a dramatic increase in the amount of marijuana people here are trying to mail out of the state.

That has been matched by an increase in the amount of drug money they have caught being mailed back into the state.

Some said they believe Colorado’s medical-marijuana boom likely plays some role, creating a legal system for growing marijuana that illicit pot-growers hope to hide behind. Under both state and federal laws, it is illegal to ship marijuana out of state.

“They’re just going to try to blend into what they perceive as a more liberal environment,” said Craig Goldberg, the acting assistant inspector in charge at the service’s Denver office.

Nationwide, postal inspectors seized 31,000 pounds of illegal drugs during the fiscal year ending in June. That is down from nearly 38,000 pounds seized the year before.

Figures on the local increase in seizures are not readily available, Goldberg said. But inspectors have certainly been busy.

For instance, when north metro-area drug agents took down a large marijuana-growing ring last month, postal inspectors helped identify shipments of marijuana the ring allegedly sent out of state. In other investigations — such as that of Mair — alert postal employees have initiated investigations by spotting — or smelling — suspicious packages.

So great is the number of marijuana mailings that the Postal Inspection Service in Colorado has created a separate process for dealing with packages suspected of containing only a small amount of drugs. Those packages are routed to a “mail recovery center,” putting the burden on their sender or recipient to come claim them, according to several search warrants filed in federal court.

Inspector Michael Nix, who leads a team of inspectors dedicated to finding drug shipments in Colorado, said his primary focus is on identifying and dismantling large distribution networks.

“Our goal is to put together criminal indictments,” Nix said.

Despite the obvious risk of detection, sending drugs through the mail provides an arm’s-length way for marijuana-growers to move drugs. Package tracking numbers offer the ability to keep an eye on the shipment.

But the practice places letter carriers in potential jeopardy, Goldberg said, because they end up unwittingly carrying around packages that could be targets for robbers.

“We have no desire for the Postal Service to be used to facilitate drug trafficking,” he said. “We want to help get drugs out of the mail for the safety of our employees.”

John Ingold: 303-954-1068 or jingold@denverpost.com