CHANGSHA - Police in central China's Hunan Province said Saturday they have launched an investigation into missing Vietnamese women -- who were bought as wives -- in its remote villages.

The probe comes after media reports said some husbands of the missing women received phone calls telling them to pay ransoms, or otherwise, the women would be sold again. About 100 purchased Vietnamese wives are missing from Hunan's mountainous regions.

Hu Qiulai and Hu Jianhe are from the same remote mountainous village in Shuangfeng County of Hunan; they lost their wives on the same day. Then two months later, they received phone calls from their wives.

"She sobbed and told me that she was kidnapped and sold to another remote village and needed 20,000 yuan ($3,130) to ransom her back," said Hu Jianhe, who bought the woman for 36,388 yuan in 2008.

The two men reported the case to local police after some hesitation, as the women, who were bought on the Sino-Vietnam border, were not their legal wives.

Hu Gengqing, Hu Jianhe's father, acknowledged that women trafficking were rampant in his county. "They were all bought from Yunnan, which borders Vietnam, and the total number (in the county) could be in dozens," he said.

There are more males than females in Chinese rural areas, as boys are preferred, so some men in poor regions resort to buying their wives as they cannot find women to marry them.

Police officers at the public security bureau in Shuangfeng County said the bureau has set up a special team to investigate the reported women trafficking and marriage fraud.

The bureau is seeking to ascertain the exact number of missing wives, as many partners may be unwilling to report the cases for fear of being accused of trafficking, they said.

Since September last year, the bureau has only received two cases in which four wives were found to be victims of trafficking, they added.