The official says a number of organized criminals, including the Mexican cartels, arrived in North Dakota in recent years from places like Southern California and other areas along the West Coast.
It's unclear which cartels are operating in the area, but the development has the FBI worried.
"We have seen a rise in narcotics investigations and a rise in human trafficking," FBI spokesman Kyle Loven said. "These are organized entities who have shown that they are present in the area. Again, because of the opportunities which exist, that's a natural thing."
In the last three years, oil production spiked. At its height, the Bakken area was producing up to 1.2 million barrels per day, according to local officials. With the production increase came more people to fill the tens of thousands of jobs created by the oil boom, many of them young people looking for opportunity.
These weren't minimum wage gigs, either. According to a U.S. Bureau of Labor Statistics report
, counties in North Dakota and Montana that were home to Bakken shale oil wells saw average annual incomes in some sectors increase by 41% or more between 2007 and 2011.
"There's a myth perpetuated because the oil prices remain (stagnant) that things have slowed down in the Bakken. That's not true. There's a lot of oil still left and people are still coming here," Chris Myers, the U.S. attorney for the District of North Dakota, told CNN.
And more young people, working better-paying jobs, mean yet another lucrative American market for Mexico's drug cartels.
Drug arrests and narcotics violations across the state increased nearly 27% between 2013 and 2014, according to the state attorney general's annual crime report.
Perhaps the hardest hit is Williston, a city of 21,000 located in the northwest corner of North Dakota. The problem is so bad that the FBI recently opened a permanent resident agency there.
It's the first new office in the United States to be opened in decades. It acts as a satellite office for the FBI's Minneapolis field office, which has jurisdiction over North Dakota, Loven said.
"The Bakken area has become a priority for the FBI, in conjunction with our state and local partners," he said.
Some of the new residents have turned to drugs, and controlled substances such as methamphetamine and heroin are especially alluring, Myers said.
While meth was popular in North Dakota well before the current oil boom, the increased demand for the drug has caught the cartels' attention, said Sylvia Longmire
, an expert on Mexican cartels and author of "Cartel: The Coming Invasion of Mexico's Drug Wars."
"There's more money in the region," Longmire said. "Mexican drug cartels see it as an emerging market they can capitalize on."
While local residents old and new are fueling demand, federal law enforcement officials noted that many of the cartels' customers come from the "all-male oil camps."
The demand is so high that drug prices reportedly are nearly double those in some big cities. With lots of money and little to do -- and no sign of oil production levels dropping precipitously anytime soon -- some of the young oil workers have turned to drugs as an outlet.
And the drug cartels are happy to be the suppliers.