Tianxi, China ? The man from family planning regularly prowled around the mountaintop village, looking for diapers on clotheslines and listening for the cry of a hungry newborn. One day in spring 2004, he presented himself at Yang Shuiying’s doorstep and commanded: “Bring out the baby.”

Yang wept and argued, but, alone with her 4-month-old daughter, she was in no position to resist the man every parent in Tianxi feared.

“I’m going to sell the baby for foreign adoption. I can get a lot of money for her,” he told the sobbing mother as he drove her with the baby to an orphanage in Zhenyuan, a nearby city in the southern province of Guizhou. In return, he promised that the family wouldn’t have to pay fines for violating China’s one-child policy.

Then he warned her: “Don’t tell anyone about it.”

For five years, she kept the terrible secret.

“I didn’t understand that they didn’t have the right to take our babies,” she said.

Since the early 1990s, more than 80,000 Chinese children have been adopted abroad, the majority going to families in the United States.

The conventional wisdom has been that the babies, mostly girls, were abandoned by their parents because of the traditional preference for boys and China’s restrictions on family size. No doubt, that was the case for tens of thousands of the girls.

But some parents are coming forward to tell harrowing stories of babies taken by coercion, fraud or kidnapping — sometimes by government officials who covered their tracks by pretending the babies were abandoned.

Parents who say their children were taken complain that officials were motivated by the $3,000 per child that adoptive parents pay orphanages.

“Our children were exported abroad like they were factory products,” said Yang Libing, a migrant worker from Hunan province whose daughter was seized in 2005. He has since learned that she is in the United States.

Doubts about how babies are procured for adoption in China have begun to ripple through the international adoption community.

The Chinese Center for Adoption Affairs, the government agency that oversees foreign and domestic adoption, rejected repeated requests for comment. Officials of the agency have told foreign diplomats that they believe abuses are limited to a small number of babies and that those responsible have been removed and punished.

For adoptive parents, the possibility that their children were forcibly taken from their birth parents is terrifying.

“When we adopted in 2006, we were fed the same stories, that there were millions of unwanted girls in China, that they would be left on the street to die if we didn’t help,” said Cathy Wagner, an adoptive mother from Nova Scotia. “I love my daughter, but if I had any idea my money would cause her to be taken away from another mother who loved her, I never would have adopted.”

The problem is rooted in China’s population controls, which limit most families to one child, two if they live in the countryside and the first is a girl. Each town has a family-planning office, usually staffed by Communist Party cadres who have broad powers to order abortions and sterilizations. People who have additional babies can be fined up to six times their annual income — fines euphemistically called “social service expenditures.”

“The family-planning people are actually more powerful than the Ministry of Public Security,” said Yang Zhizhu, a legal scholar in Beijing.

Throughout the countryside, red banners exhort, “Give birth to fewer babies, plant more trees” and, more ominously, “If you give birth to extra children, your family will be ruined.”

But the law does not give officials permission to take babies from their parents.

Some families said beatings and threats were used to force them into giving up their daughters. Others said they were tricked into signing away their parental rights.