A 2013 UN report into the trafficking of women from northern Laos found a "significant number" had disappeared inside China.
The report was released by the United Nations Inter-Agency Project on Human Trafficking and written based on data collected in partnership with the Lao Academy of Social Sciences in late 2011.
It explored patterns of human trafficking related to China in the two northern Lao provinces of Luang Namtha and Phongsaly.
A total of 14 out of the 22 villages visited, with populations numbering a few hundred, reported as many as nine such trafficking cases each. In six of the 14 villages, the reason given was for marriage to men from China, however, the report added that the number was likely to be higher.
The report said some women willingly married Chinese men, but were subsequently married off to other men, or "potentially forced in to work in the sex industry following their marriage".
"There were also reports of females being sold in China; of a girl disappearing from a market there, or of others being kidnapped and held captive by men from China," it said.
In many cases, the Lao girls went missing after marrying men from China and relocating to the husband's family. Others were approached by people at local markets in China and subsequently disappeared, while others were allegedly sold and left behind in China.
Previous anti-trafficking data compiled by the Lao government largely focused on the country's central and southern provinces, especially Vientiane Prefecture, Saravan, Savannakhet and Champassak.
According to 2011 statistics from the Ministry of Labour and Social Welfare, since 2001 1,787 trafficking victims have been officially identified; 672 in Savannakhet, 278 in Champassak, 249 in Saravan and 237 in Vientiane.