XINGTAI, China — A court in China convicted and sentenced to death on Thursday a man accused of trafficking fentanyl to the United States after a joint investigation with American law enforcement agencies.
The case, involving nine defendants in all, was a rare example of cooperation against a surge in fentanyl-related deaths that American officials, including President Trump, have blamed directly on China’s lax enforcement and even complicity in fueling a drug epidemic on American streets.
The man sentenced to death, Wang Fengxi, led an illicit network of labs that produced and shipped packages of fentanyl to American users who were able to place orders online through a dealer simply known as “Diana,” according to the Chinese and American officials.
A judge here in Xingtai, a city in Hebei Province about 220 miles south of Beijing, sentenced Mr. Wang to death after detailing a broad conspiracy to manufacture and smuggle fentanyl that evaded China’s strict controls on pharmaceutical production.
But Mr. Wang’s death sentence was suspended for two years, leaving open the possibility that it could later be commuted to life in prison. Eight other co-defendants were also sentenced on Thursday, including distributors and online sellers. They received sentences ranging from six months in prison to life.
The case started with an arrest by the Drug Enforcement Administration in New Orleans in August 2017, leading to an international investigation into a sprawling underground production network that prosecutors said Mr. Wang orchestrated.
The network included one lab and two distribution centers in Shanghai and the neighboring province, Jiangsu. They were shut down, and 12 kilograms, or about 26 pounds, of fentanyl was seized as part of the investigation, according to the officials and the court’s ruling.
“The successful outcome of this case, especially the heavy sentences to the main criminals and others, fully demonstrates the position and determination of the Chinese government to severely punish fentanyl-related crimes,” Yu Haibin, the deputy director of China’s National Narcotics Control Commission, said at a news conference in Xingtai following the court’s sentencing hearing.
He was joined by diplomats from the United States Embassy, underscoring China’s eagerness to show it was cooperating with American law enforcement to combat the fentanyl scourge. Many officials in the United States have accused China of abetting the trade.
Austin Moore, an Immigration and Customs Enforcement official working in the United States Embassy in Beijing, attended the sentencing along with other American diplomats and afterward welcomed the Chinese cooperation in the case, which he said had also resulted in arrests and indictments in New York and Oregon.
“I have one more thing to say to those who make it their business to spread illegal narcotics,” he said at the news conference, “we make it our business to find you, arrest you and hold you accountable for your crimes.”
Mr. Moore said the United States looked forward to greater collaboration as the Chinese government enforces a decision effective May 1 to classify all variants of fentanyl as controlled substances subject to strict enforcement.
That legal change, which China’s leader, Xi Jinping, promised to Mr. Trump last year, closed a loophole in the country’s laws that allowed manufacturers here to make precursors or slight variations of fentanyl that were not explicitly banned in China.
As anger rose in the United States over Chinese complicity in the epidemic, the Chinese have complained that they have been unfairly blamed for a problem that stems from pervasive drug abuse and the over prescription of fentanyl and other opioids in the United States.
Mr. Yu, sitting beside Mr. Moore in a hotel ballroom, reiterated that view on Thursday. He noted that overdose deaths in the United States had continued to rise even as China intensified its cooperation with American law enforcement agencies and tightened its own export controls.
He cited American statistics showing that customs officials had seized 536 kilograms of fentanyl since October 2018, but that only 5.87 kilograms of that came from China.
“This data does not support that China is the main source of fentanyl substances in the United States,” he said.
The sentencing on Thursday comes as aides to Mr. Xi and Mr. Trump try to finalize an interim deal in the trade war. The cooperation on display could help smooth the way, though Mr. Yu said the timing was in no way related, despite Mr. Trump’s outspoken past criticism of China regarding fentanyl.
The case on Thursday was the first fentanyl-related case to conclude, Mr. Yu said. Two other cases are still ongoing.
Claire Fu contributed research.