9Wants to Know examined a situation report from the US Department of Justice National Drug Intelligence Center, which says the Juarez and Sinaloa cartels are active in five Colorado cities.
Those cities are Denver, Boulder, Colorado Springs, Grand Junction, and Longmont.
Sylvia Longmire, author of the book "Cartel: The Coming Invasion of Mexico's Drug Wars," says the cartels mainly operate under the radar in Colorado, although they are believed to be responsible for much of the ongoing violence plaguing the border.
"What's happening along the border is crucial for folks in Denver to understand because the cartels have a physical presence in Denver and they are trafficking the majority of the drugs that are circulating throughout the city," Longmire said.
Longmire is a retired Air Force captain and former Special Agent with the Air Force Office of Special Investigations. Longmire spent six years as a senior intelligence analyst in California who focused on Mexican drug trafficking organizations and border violence issues.
The cartels in the Denver metro area may not be directly involved in street-level drug sales, Longmire says, but they do control the distribution and management aspects of the drug trade in the city.
"They are providing drugs to local gang members, they are taking care of the distribution of drugs to warehouses, to stash houses throughout different communities in Denver, making sure that they are cut, re-packaged, then sent out to smaller communities outside of the Denver area," Longmire said.
Longmire says Denver is strategically located because of the highway system. Drugs are often smuggled up I-25 from El Paso, Texas, placed in stash houses throughout the metro area, and then distributed to other cities and states.
"It's just the way Denver is laid out that makes a perfect system for transporting drugs by private vehicles, commercial vehicles. It's one of the top 7 hubs for drug trafficking activity," Longmire said.
The Mexican city directly across from El Paso, Texas, Ciudad Juarez, has been hit especially hard by cartel violence in recent years, averaging 8 drug-related murders a day. Officials estimate since 2006, drug violence has killed more than 41-thousand people in Mexico, roughly the population of Littleton.
In March, an Aurora man became a victim of the violence when he was shot 80 times in front of his wife Tania and their young son. Jake, a US citizen, had moved his family to Mexico as his wife Tania applied for her green card. Tania and their son now live in Colorado, where Jake was buried.
In February, cartel members ambushed two US ICE agents on the highway between Mexico City and Monterrey. One of the agents was shot and killed. They were in Mexico helping deal with the violence.
"It's a vicious, vicious cycle but what is happening there and happening here is very interconnected, Longmire said.
Occasionally, drug violence does flare up in Colorado. In September, Westminster Police began searching for a suspected Mexican cartel member believed to be responsible for a murder at the Toscana Apartment Complex.
A man was found dead inside his apartment. Police say the man was in the US illegally and was believed to be a member of a drug trafficking organization.
Jose Manuel Martinez-Adame is wanted for first degree murder. Martinez-Adame was given the name "Vampie" because his teeth are sharpened to look like a vampire.
Martinez-Adame was also believed to be in the United States illegally after being recently deported. Westminster Police say he has been arrested in the US multiple times., and may have since fled back to Mexico.
"I think most people are unaware," Longmire said. "The drugs that Mexican cartels are bringing to the United States are killing 11,000 people every year."
Longmire says the US will never see the extreme level of drug violence plaguing much of Mexico.
"The cartels don't want to engage in the kind of violent activity that they do in Mexico here in the United States because it is very bad for business. If they start engaging in firefights in downtown Colorado Springs or in Denver or Boulder, or if they start shooting at cops, they draw attention to themselves. And the last thing they want is to draw law enforcement attention to their drug smuggling activities because it tends to shut them down," Longmire said.
Longmire said medical marijuana has had little effect on drug cartel activity in Colorado.
"Even if they saw that loss of income from illegal marijuana, they still make money off of heroin, methamphetamine, and cocaine." Longmire said.
As domestic production of methamphetamine has declined, Longmire says cartels have seized the opportunity to profit on the deadly and highly addictive drug.
"The quality of methamphetamine, which is the number one drug threat to the Denver area, the quality of black tar heroin, the use of black tar heroin is increasing throughout many metropolitan areas throughout the U.S.," Longmire said.
9Wants to Know traveled to the U.S./Mexico border to see the affects of the ongoing drug war.
In the town of Nuevo Progreso, Mexico, only a handful of Americans were visiting the once-bustling tourist town.
Once known as a destination for inexpensive health care, authentic Mexican food, and souvenirs, Nuevo Progreso now struggles to attract Americans who perceive crossing the border to be too risky.
We found a Colorado native, Ben Long, and his girlfriend Amanda Ashley, among the handful of tourists who were visiting.
"It's a culture shock. I was born and raised in Colorado for 19 years," Long said.
Ashley's family made her take out a life insurance policy before going to Mexico.
"My good friends are freaking out right now. They're like text me whenever you cross, text me whenever you cross back, text me at every store you're at," Ashley said.
Border crossers are greeted by Mexican soldiers standing guard near the international bridge.
"Cartels killing people, decapitating people. I was a little freaked out before I got here," Long said.
Long and Ashley decided a day of fun in Mexico was worth the risk. Boarded up businesses and empty parking spaces prove they're in the minority.
"What could really go wrong?" Ashley said.
Longmire and other experts don't see an end to the fighting in Mexico anytime soon, which means border towns will also keep struggling to survive.
Tell us what you think about the battle for the border. Join the conversation on our 9NEWS Facebook page.
This is part one of a week-long series examining the battle for the border, and how it affects Colorado.
Tuesday night, you'll meet a man who is part of a family of illegal immigrants. We are with him as he is sent back to Mexico, and he tells us why he plans to cross illegally again.
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