Beth Flanders was on her way to China to adopt her 17-month-old daughter in September when she received a warning from her adoption agency: An industrial chemical that can cause kidney stones had been found in Chinese baby formula, and parents should not feed it to their new children.

Flanders’ daughter had no symptoms. But in November, an ultrasound revealed two kidney stones, which are unusual in children. Now the Los Angeles-area nurse wonders if melamine is to blame.

China’s worst product-safety scandal in years has hit home for thousands of adoptive parents, who are seeking answers about potential effects of melamine in tainted formula and other foods. Many are requesting medical tests for children even if they were adopted long before the contamination became known.

The American Society of Pediatric Nephrology recommends ultrasounds and other tests for infants exposed to tainted formula in late 2007 and 2008 if they have blood in their urine, kidney pain, unexplained crying or other symptoms.

With no studies of melamine’s effect on humans, some doctors say they aren’t sure if other children should be tested as well.

“Nobody’s really going to know what the best thing to do is at this point, which is the scary part,” said Flanders, whose daughter is from China’s Jiangxi province, where tainted formula was found, and was not eating solid foods when she was adopted. “We’re all in the dark together.”

Flanders adopted her daughter just days after the China Health Ministry ordered a nationwide probe of milk powder linked to kidney stones in infants. China says six babies likely died and nearly 300,000 suffered urinary problems from drinking melamine-tainted milk powder.

The nitrogen-rich chemical used in the production of plastics was dumped into watered-down milk so that higher protein levels would register during food-quality tests. It has since surfaced in eggs, milk, candy and other food products, triggering product recalls worldwide.

Melamine also was found in exported pet food blamed for killing dogs and cats in North America in 2007.

The Chinese government has reported that at least one dairy, Sanlu Group Co., knew as early as 2007 that its products were tainted with melamine and that company and local officials tried to cover it up. The general manager of Sanlu pleaded guilty to charges in the scandal, and trials have begun for seventeen others blamed for the contamination. At least four could face the death penalty, according to the official Xinhua News Agency.

The attention on the melamine crisis has focused primarily on children still in China, where thousands of parents have sought tests and treatment. In the U.S., parents of children adopted from China waited weeks for medical guidance specific to adoptees, and many pursued testing after consulting their pediatricians or adoption agencies.

Keith Wallace, executive director of Families Thru International Adoption in Evansville, Ind., says there’s no way to know for sure if a child was exposed to melamine in baby formula or other foods while living in China.

Even orphanages using a “safe” brand of formula may have supplemented their supplies with donated formula that could have been tainted, the agency says. Wallace said his staff has urged parents to consult their doctors if they are concerned, regardless of how long their child has been home.

The American Society of Pediatric Nephrology says adoptees are unlikely to be affected unless they were drinking tainted formula in late 2007 or 2008. It does not recommend testing for children who aren’t exhibiting symptoms of kidney stones or urinary problems.

Dr. Michael Somers, a pediatric nephrologist at Children’s Hospital Boston and member of the nephrology group, said even children exposed to melamine may be fine once it is removed from their diet.

“They’ve been away from the contaminant for so long that they were likely to probably have resolved all of this on their own,” Somers said.

Dr. Debbi Borchers, a Cincinnati pediatrician, said not every child adopted from China needs to be tested, but that doesn’t mean the melamine issue should be ignored.

“It doesn’t hurt to be cautious,” said Borchers, the mother of three daughters adopted from China between 1994 and 2000. “At the same time, you don’t want overkill.”

Flanders doesn’t plan to have her 6-year-old daughter, adopted from China at 10 months, tested at this point.

But her younger daughter’s kidney stones are large, and she is awaiting more medical tests to determine if surgery to remove them is necessary. In the meantime, Flanders is seeking more information about the issue.

She joined an online group for melamine concerns started by Kathy Demetrius, an adoptive parent from Warren, Mass. The group registered 1,000 members in just over a month and consists of parents and doctors who share test results and other information.

“We want to be there for each other in case things start to arise later on in life,” said Demetrius, who adopted her 10-year-old daughter from China a year ago.