The manufacturer of zeranol, an animal growth stimulant whose presence has been found in blood tests of Puerto Rican children with abnormal sexual development, said yesterday the results are "statistically impossible" and will be proved wrong by further government tests.

"If a child has high levels in the blood, they would have to be eating pellets for breakfast food," said Dr. Bruce Martin, a scientist in the corporate and regulatory affairs department of the International Minerals and Chemical Corp. of Terre Haute, Ind., which produces zeranol.

The product, sold under the trade name Ralgro, is the only synthetic estrogen approved for use in the United States.

Recent preliminary tests by the U.S. Centers for Disease Control found zeranol in four of 19 blood samples of afflicted children. Further tests are underway.

Martin said that zeranol residues in meat in the United States and elsewhere never have exceeded the 20 parts per billion limit set by the U.S. Food and Drug Administration. "I don't think there's any chance that meat from implanted animals could cause these problems in the children," he said.

Zeranol was approved by the FDA in 1969 and is used by growers to fatten cattle and sheep. A stronger synthetic estrogen, diethylstilbestrol (DES), was taken off the market in 1979 because of its cancer-causing properties.

Dr. Lester Crawford, director of the FDA's Center for Veterinary Medicine, said his agency has begun a daily monitoring of the Agriculture Department's meat testing program in Puerto Rico. "We don't have any pattern of public health concern with zeranol, not like we had with DES," he said.