The US Drug Enforcement Agency has now walked back statements it made this week about the trafficking of marijuana grown in the US to buyers in Mexico, after being met with skepticism by other law enforcement agents and experts and being pressed to divulge more information on the allegedly burgeoning problem.

The claim that Mexican drug cartel members were taking US-grown weed and selling it at a premium to Mexican customers first emerged this week in a broader NPR report on the effects of legalized marijuana on the illicit drug trade. NPR reported that the worth of Mexican marijuana had declined as high-grade US-grown weed had become more favorable to US customers.

Lawrence Payne, a spokesman for the Drug Enforcement Agency, told NPR that Sinaloa cartel members were now taking American pot and bringing it back across the border to sell at a premium to Mexican customers.

That claim was then repeated by Payne in a US News report, in which he said that "traffickers who are operating in the US are securing marijuana in the US that is much higher quality and more expensive for the purpose of smuggling back into Mexico for sale and distribution."

But other drug enforcement agents asked about the trend by VICE News said they would be surprised if it is true.

"We have not heard that," said Tom Gorman, director at the Rocky Mountain division of the Office of National Drug Control Policy's High Intensity Drug Trafficking Area program (HIDTA). "We have not seen that, and have not heard about our marijuana being grown here going back to Mexico. We know it's being diverted out of Colorado to other states, but we've not been able to confirm it's going back into Mexico."

"No," said William Ruzzamenti, director of California's Central Valley division of HIDTA, when asked if he'd seen marijuana grown in California being trafficked back to Mexico. "I'm a bit surprised, actually. Nothing should ever surprise you in the drug world, but as far as I know we haven't seen any of that."

"We believe a tremendous amount of marijuana is being diverted out of the state of Colorado, but whether it's actually going down to Mexico, I don't know," said Marc Vasquez, a former investigator in Colorado's Medical Marijuana Enforcement Division and now chief of police in Erie, Colorado. "It's a lot easier to do that and ship it across state lines as opposed to the international border."

Seth Crawford, a sociologist at Oregon State University who researches the marijuana marketplace, said that the idea of US-grown marijuana being smuggled into Mexico didn't make sense in the current market conditions.

"It goes against everything we know about cartels and the US," Crawford told VICE News. "The quality up here, because of the way they have to produce it in in large fields, is nowhere near what it could be and the ecology is better in Mexico."

"Anyone who is a serious researcher when it comes to drug policy takes anything the DEA says with a grain of salt."

While skeptical, Vasquez, Ruzzamenti, and Crawford all said that it is entirely possible that marijuana trafficking had reversed directions. Crawford went the furthest, saying "it would't surprise me if there was a small flow for high end consumers."

Payne, when pressed for more information about this new development drug in trafficking, clarified to VICE News that it is not actually a burgeoning trend. He said that it was, in fact, a single incident that is under investigation by the DEA.

"If you are talking about marijuana flowing south to Mexico, I only referred to one example we know of," Payne said. There was no information to share on this specific case, he told VICE News.

"[There is] one single example that we know of related to US marijuana traveling south into Mexico, based on intelligence gathered during the course of an ongoing investigation. I have said nothing about any sort of trend. Again, one single example," he told VICE News.

"So people are skeptical that on one single occasion, drugs actually went from the US into Mexico?" Payne asked, referencing Vasquez, Ruzzamenti, and Crawford's disbelief.

The discrepancy in Payne's statements earlier this week and those made to VICE News lends itself to the sort of criticism often leveled at the DEA by marijuana researchers and advocates: that the agency puts out information to serve its own interests.

"Anyone who is a serious researcher when it comes to drug policy takes anything the DEA says with a grain of salt," Crawford said. "They obviously have a vested interest, and I'm not blaming them, but we are cautious in our interpretation of their official data."

Crawford pointed to an example in which the DEA published annual statistics on the number of marijuana plants seized each year to show how much had been taken out of the marketplace, but were found to be including wild marijuana plants, or "ditchweed" in their tallies — plants that weren't actually being used to cultivate drugs. Some 98 percent of the total was ditchweed, Crawford said of the data.

"The numbers make you shake your head and go, 'what are you doing?'" Crawford said.

Mason Tvert, spokesman for the Marijuana Policy Project, said that the DEA often gets away with making statements without backing them up with evidence, and often does so in a political capacity to sway opinion.

"The DEA has long advocated for maintaining marijuana prohibition," he said. "You don't really see the DEA talking about the positive. They've not traditionally proven to be an objective agency."

Both Crawford and Tvert pointed out that the DEA has a reason to want to sway public opinion toward keeping marijuana illegal.

"Marijuana is by far and away the most popular currently illegal substance in this country. Other illegal drugs are used at exceptionally lower rates. If all of a sudden the DEA is no longer tasked with handling marijuana, and it moves to the ATF like other substances, the DEA stands to lose a significant amount of funding, and they wouldn't have nearly as much work to do," Tvert said.

"There's a significant body of literature that addresses that. Any type of rule enforcement organization, and particularly law enforcement, have to demonstrate they're doing a good job and espouse the virtue of what that job happens to be," Crawford said.