Authorities are investigating a Taiwan-based surrogacy company on charges of human trafficking in an Internet racket that may have forced some Vietnamese women to breed for cash.

Late last month, police raided a Bangkok home and found 15 Vietnamese women, seven of whom were pregnant. Some of the women said they had been lured to Thailand with promises of well-paying jobs, then had their passports seized by the Babe-101 Eugenic Surrogate firm.

Thai law forbids a mother to sell her baby, and the Anti-Human Trafficking Act outlaws exploitation of people for money.

“The Vietnamese women were not forced to work here,” said a woman who answered the company’s Bangkok telephone number Saturday. She spoke Mandarin Chinese and refused to give her name or position in the company. “They agreed to work, because earlier some of the Vietnamese women who worked with us went back to Vietnam and told their friends and referred them to us also, to do this.”

Asked whether the company kept the women’s passports, she said: “Yes, the company keeps the passports, but when the women want to use them, the company will give the passports back to them.”

Some Thai news reports said police arrested a Taiwanese man, Siang Lung-lor, on charges of human trafficking and sheltering illegal immigrants. He was described as a Babe-101 executive and manager of the Bangkok home.

But the Chinese-speaking woman said Mr. Siang was not under arrest and was still in Thailand. Mr. Siang was not available for comment.

“From the government’s view, these women are the victims of human trafficking [and] require suitable help and support,” human rights lawyer Surapong Kongchantuk said in an e-mail.

Officials from the Public Health Ministry, the Foreign Ministry, the Vietnamese Embassy, the Thai Immigration Department and the Royal Thai College of Obstetricians and Gynecologists were coordinating a response.

“It is critically important that there be effective cross-border law enforcement cooperation to ensure that all persons involved in this apparently criminal enterprise be held accountable,” Phil Robertson, deputy director of New York-based Human Rights Watch’s Asia Division, said in an e-mail.

The company apparently was administered in Taiwan and offered surrogate homes in Thailand and Cambodia, plus a representative office in Vietnam.

On its website, Babe-101 Eugenic Surrogate offers $5,000 to women seeking to be surrogate mothers and asks whether they have “double-fold” or “single-fold” eyelids because some customers are concerned about how their baby’s eyes would appear.

In addition, the company charges each client $35,000 to rent a surrogate mother and pay for a sperm or egg donor who is either “Eastern race” or “Caucasian” with a complexion of “Yellow,” “Caucasian,” “Brown,” “African” or “Red.”

The website notes that Babe-101 does not employ Thai women as surrogates, but it does not specify the nationalities of its surrogate mothers.

“According to … the Civil Registration Act, one may claim to be the mother if she is the one who gave birth to that child,” Mr. Surapong said. “Once the mother sold her child to others, she may be charged with human trafficking.”