Two months after disputing similar findings, U.S. and Puerto Rican health officials have released evidence that the blood of Puerto Rican children afflicted with abnormal sexual development contained traces of a growth stimulant used to fatten cattle and sheep.

In a statement based on preliminary results of new tests by the U.S. Centers for Disease Control, the secretary of health for Puerto Rico announced that four of 19 blood samples from afflicted children showed the presence of zeranol, an estrogen-like growth stimulant implanted in animals worldwide.

The secretary, Jaime Rivera Dueno, said the possible zeranol contamination of the food chain might be the cause of the children's physical problems. CDC officials said yesterday that it was premature to make such a link.

Dr. Jose Cordero, an epidemiologist in the CDC's birth defects section, said that it was not known whether the high zeranol levels were limited to children in Puerto Rico.

Zeranol, which is sold under the trade name Ralgro, has been on the market more than 20 years and is widely used in this country. "No one has tested this in the United States. We don't know whether we'll find it in U.S. children," Cordero said. "We're trying to find out what these preliminary tests mean."

The director of emergency programs within the U.S. Agriculture Department's Food Safety and Inspection Service said yesterday that the agency would increase the number of meat samples taken and the types of tests performed in Puerto Rico, including a test for zeranol. Now, meat is tested only for the presence of pesticides.

"We want to find out whether the meat and poultry supplied to the people of Puerto Rico contain illegal residues," said Earl Montgomery, director of emergency programs for the service.

It is estimated that 3,000 children on the island -- some as young as 9 months -- have developed breasts, begun menstruation and had their growth stunted, according to two Puerto Rican pediatric endocrinologists who have been treating the children since the late 1970s. The doctors blamed estrogen growth stimulants administered to animals.

"The CDC was withholding tests in order to make me look bad," Dr. Carmen Saenz, one of the two doctors, said in an interview yesterday.

At a scientific meeting in Puerto Rico two months ago, the Puerto Rican health secretary and CDC officials criticized a report by one of the doctors that high levels of zeranol was found in five blood samples. A five-member commission appointed by CDC and the Puerto Rican government two years ago said that their $1 million study was inconclusive about the cause of the condition.

However, Saenz -- who has waged a campaign to bring attention to the children's health problems -- presented evidence at the conference that five of six blood samples she had sent to a French biochemist had high levels of zeranol.

The biochemist, Robert Morfin, then at the University of Science in Brest, has developed a sophisticated method of detecting zeranol in the blood.

But Rivera Dueno, the health secretary, countered Saenz's findings with a telegram to the CDC from Morfin's successor at the university that shed doubt on Morfin's findings.

After the scientists' conference, Saenz and her husband, a local surgeon, traveled to Europe at their own expense to meet with Morfin, by then sabbatical in Morocco. He signed an affidavit affirming the initial results' authenticity, but said more tests were needed.

"There was some confusion at the meeting," said Dr. Godfrey Oakley, chief of CDC's birth defects branch. He said that prior to the meeting, Morfin's successor had told CDC that the initial tests were positive for zeranol "but when the tests were cleaned up, the samples were no longer positive."

Oakley said that the CDC also questioned Saenz's results because of a zeranol analysis on the children's blood that a Minnesota researcher performed for the CDC in May. He said that after the September conference, the CDC decided to perform new tests in its own laboratory. These tests found zeranol present.

The CDC's Cordero said the new tests "were in the process of being done while the September meeting was going on."

Zeranol is manufactured by International Minerals and Chemical Corp. of Terre Haute, Ind. Pellets retail for about $2 each, and two to three pellets are implanted under the ears of cattle and sheep. Growers are supposed to withdraw the pellets 60 days before animals are marketed, but the USDA's Montgomery said the government does not check to see if this is done.

"We don't have control over the livestock before they get to the federal plants," he said. "That's done largely through education programs with farmers, depending on them to follow the instructions on the implant or feed."

There are about 22 federally inspected livestock and poultry plants in Puerto Rico and about 80 processing plants that receive meat from the United States, South and Central America and elsewhere, Montgomery said.

Saenz charged yesterday the CDC was trying to block an investigation into the public health problem by the National Institutes of Health, which is planning to fly 15 of the affected Puerto Rican children here for examination this month and in January.

Oakley confirmed that he had asked Dr. Ora Pescovitz of the Developmental Endocrinology Branch of the National Institute of Child Health and Human Development not to bring children in unless a new CDC commission assigned to the problem chose the cases to study.

"I thought a better way to select her patients is to have them go through the committee," Oakley said. "It's a complicated situation. It would be better to use this expert committee to standardize the definition of premature thelarche breast development ."

Oakley said that he and Pescovitz had not reached agreement on whether she should proceed with her study of the affected children.