The first human embryo editing has been accomplished in Oregon, according to a new report.

The DNA of dozens of one-cell embryos was altered by the CRISPR method – and the cells developed for several days afterward, but matured no further, according to those familiar with the results who spoke to the MIT Technology Review.

Unlike previous efforts in China and elsewhere, the early-editing technique by Shoukhrat Mitalipov of the Oregon Health and Science University has apparently proven successful, the report claims.

The results are apparently pending publication, according to the report.

CRISPR has previously shown errors in manipulating human cells, since not all the cells in an embryo do not adopt the genetic changes. But with the latest experiments, the single cells have apparently created “germ-line” changes that would basically completely alter the DNA, the report adds.

Mitalipov previously was known for cloning the first monkeys a decade ago, and creating human embryos through cloning in 2013.

The human-embryo editing was first accomplished in China in 2014 and 2015. But last year, Swedish researcher Fredrik Lanner at the Karolinska Institute also told reporters he had been customizing the DNA of human embryos – while not allowing them to mature past one week.

The limits to genetic engineering of human cells have not been established. The U.S. had not engaged in the kinds of boundary pushing of China and Sweden – until now.

But an American report published in February urged the need to progress forward with the research.

“Human Genome Editing: Science, Ethics and Governance” was published by the National Academy of Science, after two years of work and analysis.

The Committee on Human Gene Editing recommended a series of general values: transparency, wellbeing of people, fairness, and responsible science, in an age of DNA manipulation. They explicitly urged caution when it came to “germ-line” editing, since the heritable changes should be considered for compelling reasons. Overall, their recommendation was that genetic engineering should be tightly regulated – and it should focus on treating disease and not enhancing the human species.