BEIJING (AP) ― Chinese police on Tuesday announced the arrests of 23 people as part of a joint U.S.-Chinese investigation into a gun trafficking ring that smuggled dozens of firearms into the country.

The arrests announced by the Ministry of Public Security follow the detention of three men in the United States last month in connection with the scheme. They included Joseph Debose of North Carolina, a staff sergeant in a U.S. National Guard special forces unit, along with two Chinese nationals.

Debose was arrested on May 20 in a sting operation when he arrived with another shipment of guns for export to China and had been armed with a loaded .45-caliber pistol, according to the U.S. Attorney’s Office in the Eastern District of New York.

The smuggling ring defaced serial numbers on the guns to disguise their origin, but U.S. investigators working with Shanghai police were able to trace some of them to Debose.

“This level of cooperation between American law enforcement officials and authorities inside mainland China is a sign of optimism and could lead to even greater law enforcement cooperation in the future,” the U.S. Embassy in Beijing said in a statement Tuesday.

The Chinese ministry said the latest arrests took place in 16 different provinces and cities and led to the seizure of 93 weapons, large amounts of gun parts and more than 50,000 bullets.

It said the investigation stemmed from the detention in August last year of a 32-year-old Chinese man, Wang Ting, at Shanghai’s Pudong Airport after he attempted to claim an overnight delivery package that was labeled as stereo equipment but actually contained nine handguns and additional parts.

Firearms are tightly controlled in China and private ownership is for the most part illegal. Periodic campaigns aim to round up trafficking rings and seize and destroy illegal weapons.