Lo Thi Dien, 33, and her husband Giap Van Long, 32, have been placed under arrest, Lang Son Province's police said Monday.

The police and patrol officers in Cao Loc District at the China border stopped the couple's car last Wednesday as it headed to the border and discovered the girls inside.

Initial investigation found the couple have been smuggling many young Vietnamese women to China to find jobs or marry to Chinese men, Giao Thong newspaper reported.

No information has been released on whether the girls have been detained for further investigation or have been returned to their hometowns.

Police said that the case is being investigated further.

About 80 percent of human trafficking victims in Vietnam end up in China, according to the Ministry of Public Security.

Most cases are from northern border provinces such as Lao Cai, Ha Giang, Dien Bien, and Quang Ninh, and most of the victims are women or children.

China, the world’s most populous country, suffers from one of the worst gender imbalance rates due to its one-child policy and illicit abortion of female fetuses by parents wanting sons. This has led to increasing trafficking of Vietnamese women and baby girls to the neighboring country.