How does fentanyl get into the US?

U.S. President Donald Trump has announced the imposition of long-threatened 25% tariffs on goods from Mexico and Canada, as well as new 10% tariffs on China. The Trump administration's stated reason is the failure of these countries to stem the export of chemicals used to produce the powerful opioid fentanyl.

The U.S. has long accused Chinese companies of knowingly supplying chemicals to groups involved in fentanyl production. China has responded with retaliatory tariffs. The White House also accuses Canada and Mexico of failing to stop criminal groups from smuggling fentanyl into the U.S.

China has announced a 15% tariff on U.S. goods in retaliation. Canada has announced 25% tariffs on $30 billion worth of U.S. goods and plans to impose tariffs on an additional $125 billion worth of goods within the next 21 days. Mexico is expected to respond later on Tuesday.

Fentanyl is a drug synthesized from multiple chemicals. U.S. regulators approved it for medical use as a painkiller in the 1960s, but it has since become a leading cause of opioid overdose deaths in the U.S. According to the U.S. Centers for Disease Control (CDC), over 74,000 Americans died in 2023 after taking mixed drugs containing fentanyl. Fentanyl is often mixed with other illicit drugs, leading many users to be unaware that the substance they are taking contains fentanyl. A dose of just two milligrams of fentanyl – roughly the size of a pencil tip – can be fatal. Over the past decade, the global fentanyl supply chain has expanded, making it more difficult for law enforcement and policymakers to control. China is a major source of precursor chemicals used to manufacture fentanyl.

According to data released by U.S. Customs and Border Protection (CBP), the U.S. has seized 7,793 pounds (3,534 kg) of fentanyl since September. Almost all (98%) of the fentanyl was intercepted at the southwest border with Mexico. Less than 1% of fentanyl seizures occur at the northern U.S. border with Canada. The remainder comes from maritime routes or other U.S. checkpoints. The U.S. Drug Enforcement Administration (DEA) says that Mexican criminal organizations, including the Sinaloa Cartel, play a key role in producing and trafficking fentanyl, methamphetamine, and other illicit drugs into the U.S. The chemicals used to make fentanyl are sourced from China by traffickers and processed into finished products in labs in Mexico, before being smuggled into the U.S.

According to the U.S. Drug Enforcement Administration, the Sinaloa Cartel uses a variety of tactics to conceal shipments entering Mexico, such as hiding chemicals inside legitimate commercial goods, mislabeling containers, using shell companies, and shipping through third-party countries. The Trump administration has accused the Mexican government of colluding with drug cartels. Mexican President Claudia Sheinbaum has called these claims "slanderous." Last December, shortly after Trump threatened to impose tariffs on Mexico, Mexican security forces announced the seizure of the largest amount of fentanyl ever recorded, equivalent to about 20 million doses. In response to the U.S. tariff threat, the Mexican government launched "Operation Northern Border" on February 5, deploying 10,000 National Guard troops along the U.S.-Mexico border. In its latest government announcement, the Mexican government said that 55.9 kg of fentanyl had been seized in the month since the operation began.

In 2019, China listed fentanyl as a controlled narcotic and later added some chemicals used to make fentanyl to the list. Nevertheless, the trade in other chemicals involved in fentanyl manufacturing – some of which may have legitimate uses – remains unregulated, as those involved in the trade find new ways to evade the law. A review of several U.S. indictments suggests that some Chinese chemical companies have been selling chemicals, including controlled chemicals, while knowing that the chemicals were intended to manufacture fentanyl. These indictments contain details of communications between undercover agents and Chinese manufacturers. Dozens of indictments reviewed by BBC Verify detail cases in which Chinese manufacturers provided instructions via encrypted platforms and cryptocurrency payments on how to make fentanyl from the products they sold.

“So, you see these huge loopholes where criminals engage in activities that sell legitimate products, but they knowingly sell them to criminal entities,” said Vanda Felbab-Brown, a senior fellow in foreign policy at the Brookings Institution. China said in a statement that it has the strictest drug laws in the world and has previously conducted joint operations with the U.S. "The U.S. needs to look at and address its own fentanyl problem," the statement said. While China remains a major source of chemicals for making fentanyl, the U.S. Drug Enforcement Administration has also identified India as an emerging major source of these chemicals. In a January 2025 U.S. indictment, two Indian chemical companies were accused of supplying chemicals used to make fentanyl to the U.S. and Mexico.

President Trump has accused Canada (as well as Mexico) of allowing "large numbers of people to come in and bring fentanyl in" to the U.S. According to U.S. Customs and Border Protection data, only about 0.2% of all fentanyl seized entering the U.S. is seized at the Canadian border, with almost all the remainder being confiscated at the U.S.-Mexico border. But in January, Canada's financial intelligence agency reported that Canadian organized crime groups are increasingly involved in fentanyl production, importing chemicals and lab equipment used to make fentanyl from China. The trade in fentanyl is two-way. In the first 10 months of 2024, the Canada Border Services Agency reported seizing 4.9 kg of fentanyl entering from the U.S., while U.S. Border Patrol intercepted 14.6 kg of fentanyl coming from Canada. Last December, Canada pledged C$1.3 billion ($900 million; £700 million) to combat fentanyl and strengthen border security. On February 11, Canadian Prime Minister Justin Trudeau announced the appointment of Kevin Brosseau as Canada's Fentanyl Coordinator.