On December 19, U.S. Senator Ron Wyden reached out to seven maritime shipping companies to investigate possible links between their operations and fuel smuggling related to cartels between the U.S. and Mexico. He requested details on how these companies ensure their tankers are not used for illegal fuel transport, according to letters seen by Reuters.

The letters, sent by Wyden, who is a senior member of the Senate Finance Committee, were dated Friday. Recently, stolen crude oil and smuggled fuel have become the second-largest source of income for Mexican cartels, following drugs, as noted by the U.S. Treasury.

Criminal groups have strategically embedded themselves into North America's energy sector, cleverly managing the logistics of moving oil products by truck, rail, and tankers. This demonstrates the creativity of Mexico’s cartels, which have been known to recruit various legitimate oil industry players for assistance in acquiring and transporting these products, sometimes without their knowledge and other times with their full participation, according to law enforcement sources.

"I want to ensure that both the shipping companies and the U.S. government are doing everything possible to cut off this source of income," Wyden told Reuters via email. "These letters are the initial step in my effort to better understand how these criminal operations work and where current controls are lacking."

Wyden's letters referenced a Reuters investigation that outlined how the alleged scheme functions and exploits gaps in the expansive and intricate U.S. energy sector, impacting numerous entities including oil companies, shipping firms, and government agencies.

The letters were sent to seven major players in the global oil tanker industry: Torm, International Seaways, Norden, CMB.Tech, Frontline, Teekay, and Scorpio. Wyden is asking for detailed responses by January 10, 2026, regarding the due diligence procedures each company employs to ensure their oil tankers are not involved in transporting illegal fuel.

To date, none of the companies have faced any charges.

Torm was managing two vessels that were reportedly linked to oil smuggling earlier this year, according to the October 22 Reuters investigation, which cited various documents and security sources.

CMB.Tech stated that it implements due diligence, adheres to know-your-customer standards, and complies with all relevant regulations. The Belgium-based firm confirmed it would respond to Wyden’s inquiries.

Norden acknowledged receipt of Wyden's letter and stated that its maritime operations strictly follow applicable laws.

The other companies did not provide immediate comments regarding Wyden's queries.

According to the agency, Mexican cartels have increasingly infiltrated the multi-billion dollar fuel smuggling operation between the U.S. and Mexico.

This operation revolves around evading taxes. Mexico imposes a tax known as IEPS on imported goods like diesel and gasoline. Criminals escape this tax, which can exceed 50% of the cargo’s value, by mislabeling foreign fuel as another product type that gets exempted from the fee. A single tanker load can help avoid millions in taxes, as reported by Reuters based on standard tax rates and typical cargo volumes.

The Jalisco New Generation Cartel, noted for being one of Mexico's most dominant and violent groups, stands out in the realm of fuel and crude oil smuggling, being the only cartel known to use tankers, according to security sources in both Mexico and the U.S.

The smuggling of fuel has escalated to the point where these illegal imports now make up about one-third of Mexico’s diesel and gasoline market, affecting profits of major players in the oil sector, as indicated by five former and current Mexican government officials earlier this year. The illegal fuel entering Mexico is estimated to be worth over $20 billion annually, according to one person involved in assessing the size of this underground market.

"The extent of these illegal fuel smuggling operations is shocking," Wyden mentioned in the letters. "Addressing this illegal industry is crucial to limiting the cartels’ capacity to manufacture and distribute fentanyl, cocaine, and other dangerous drugs in the U.S., and the global shipping industry must contribute to ending these unlawful practices."