Vietnam and the U.S. have announced that cooperation on cross-border crime has led to a U.S. grand jury indictment of an American teacher accused of traveling to the Southeast Asian nation to have sex with minors.

The U.S. Attorney’s Office in the Northern District of California alleged that the teacher, Paul Marshall Bodner, of San Francisco, California, “met Vietnamese boys as young as 11 or 12 years old and engaged in sex acts with them at a hotel located in Ho Chi Minh City when he traveled to Vietnam” in the period from July 2015 to August 2016. If convicted he faces up to 30 years in prison and a fine of $250,000.

U.S. ambassador to Vietnam, Daniel J. Kritenbrink, said the investigation was aided by close cooperation between the two nations, which normalized relations in 1995, 20 years after the Vietnam War, and have since become partners on security, trade, and cultural issues.

“In this instance, strong collaboration between the Homeland Security Investigations office in Ho Chi Minh City and Vietnam’s Ministry of Public Security have brought multiple child victims one step nearer to finding closure,” said Kritenbrink on Thursday. “This arrest also underscores how the United States and Vietnam can work together effectively to combat child exploitation.”

Human trafficking has become a higher priority for Vietnam since October of last year, when 39 of its citizens were found dead in a container truck in the United Kingdom, believed to have suffocated to death after being trafficked from Vietnam. Trafficking victims from the Southeast Asian nation range from workers tricked into bondage abroad, to young women sold as brides, such as to Chinese or Korean husbands.

The Blue Dragon Children's Foundation, based in Hanoi, works to help sex trafficking victims, including both those who are sold abroad as well as those forced into sex work domestically. However the new coronavirus has complicated the foundation’s efforts in recent weeks. Vietnam and China have effectively shut down their 1,200 kilometer land border. That makes it harder for traffickers to send Vietnamese to China, but it also makes it harder to rescue victims and return them home.

“Blue Dragon has temporarily suspended rescue operations of human trafficking survivors from China, as the current restrictions to travel within and from China prevent our rescue team from conducting operations as usual,” the organization said in a statement. “On the legal front, Blue Dragon will use this pause to work on child sexual abuse cases and prosecutions of traffickers.”

The foundation usually assists with prosecutions of traffickers and sex offenders in Vietnam.

In contrast, the charges against Bodner, brought by a U.S. federal grand jury, mark a rare instance of joint investigations between Vietnam and the U.S. that lead to an indictment.

The 64-year-old was charged with three counts of travel with intent to engage in illicit sexual conduct, as well as one count of engaging in illicit sexual conduct in a foreign place.

The grand jury indictment was unsealed the day of a pre-trial hearing for Bodner on Feb. 14 but a trial date was not announced.

In addition to law enforcement, Vietnam and the U.S. have also increased their cooperation in defense. Last year the U.S. conducted its first ever joint naval drills with the Association of Southeast Asian Nations, a bloc of 10 nations with a rotating chair that is being hosted this year by Vietnam.

The U.S. also gave Vietnam's Coast Guard six patrol boats worth $12 million in 2019, part of ongoing efforts to shore up Hanoi’s defenses in the South China Sea. Vietnam has territorial claims there that are being challenged by China, whose growing power is also pushing the U.S. and Vietnam closer together.