Fentanyl claimed the lives of 75 Ohioans in 2012, but by 2015 that number jumped to a staggering 1,155.

Ohio is now the overdose capital of the United States in no small part because of the rise of fentanyl. Per the Drug Enforcement Agency, Ohio had 3,861 positive lab tests for fentanyl in 2015, more than any other state. Massachusetts had the second most with 2,556 and Pennsylvania had the third most with 897. Nationwide that year U.S. law enforcement agencies seized a record 368 pounds of fentanyl. The drug is 50 times more powerful than heroin and even two milligrams is a potentially lethal dose according to the DEA.

Fentanyl was first introduced more than 50 years ago and was approved for treating severe pain in the early 1990s, typically for advanced cancer patients. It’s since become a more commonly prescribed painkiller. U.S. doctors wrote 6.65 million fentanyl prescriptions in 2014.

Commonly prescribed in transdermal patches or lozenges, it can be “diverted from its medical applications and misused by removing the gel contents from patches and injecting or ingesting the drug, or compressing it into pill form,” according to a report from the U.S.-China Economic and Security Review Commission.

Though there is some pharmaceutical fentanyl being diverted from the legitimate market, the DEA said that makes up “only a small portion of the fentanyl market.”

China is the primary source of fentanyl in the United States. The U.S.-China Economic and Security Review Commission’s recently released report examines how “China’s illicit chemical production and inefficient U.S. and international counternarcotic efforts” created the stark increase in fentanyl-related deaths.

“China is a global source of fentanyl and other illicit substances because the country’s vast chemical and pharmaceutical industries are weakly regulated and poorly monitored,” the report states. “Chinese law enforcement officials have struggled to adequately regulate thousands of chemical and pharmaceutical facilities operating legally and illegally in the country, leading to increased production and export of illicit chemicals and drugs.”

Some of the fentanyl comes straight to the United States from China, while other shipments come in from China to Mexico (and to a lesser extent) Canada before making its way into the U.S.

The report said China exports a number of different fentanyl products into the U.S.: raw fentanyl, precursors, analogues, fentanyl-laced counterfeit prescription drugs like oxycodone, pill presses and other machinery necessary for fentanyl production.

“Chinese chemical exporters utilize various methods to covertly ship drugs to the Western hemisphere, including sending illicit materials through a chain of forwarding systems, mislabeling narcotics shipments and modifying chemicals so they are not controlled in the United States,” the report stated.

The exported products are sent to small-scale distributors and criminal organizations across the United States who package and sell the product.

According to the DEA, Mexico is rarely the final destination for the fentanyl imported from China. Most is repacked and sent into the U.S. Cartels are the primary conduit, purchasing it and trafficking it either alone or mixed with other drugs like heroin across the border. In 2015 U.S. border agents seized around 200 pounds of fentanyl and other synthetic opioids from Mexico. They confiscated just eight pounds the year prior.

The U.S.-China Economic and Security Review Commission report said to reduce flows of fentanyl and similar substances to the U.S., the country’s regulators should “reexamine policies and procedures for banning and controlling dangerous chemicals and work with their Chinese counterparts to improve regulations governing chemical exports.”

The two countries have worked together in recent years to address the problem. In 2015, China added 116 synthetic products, including six fentanyl products, to its list of controlled substances. There are now a total of 19 fentanyl-related products under control in China, but there are still some not on the list, including two of the most common precursor chemicals.

In October 2016 then-Secretary of State John Kerry asked for those two chemicals to be added to the list of controlled substances under the 1988 Convention against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.

Kerry asked the UN Commission on Narcotic Drugs to be ready to make a decision on controlling fentanyl precursors during the next meeting in March. China would be bound to abide by the commission’s ruling as it is an original signer to the 1988 UN Convention.

“Last year, over a period of just two months, in my hometown of Cincinnati more than 1,000 overdoses were traced back to the influx of these synthetic drugs,” Senator Rob Portman, R-Ohio, said in a statement. “This new report confirms that China is the global source of fentanyl and that Chinese exporters use various methods to covertly ship drugs into the United States, including through the mail.”

Portman said in his statement he plans to reintroduce the STOP Act, which he introduced last year.

The Synthetics Trafficking & Overdose Prevention Act is aimed at preventing synthetic drugs coming into the country through the mail system.