Chinese geneticist He Jiankui on Wednesday said he was proud of creating the world’s first genetically edited babies and that another volunteer is pregnant as part of his research, Reuters reported. On Sunday, He Jiankui had claimed that he had altered the genes of twins born earlier this month.

An associate professor at Southern University of Science and Technology in Shenzhen, He Jiankui on Wednesday was addressing around 700 people at the Human Genome Editing Summit at the University of Hong Kong.

“For this case, I feel proud,” he said, when challenged by his peers. “I feel proudest.” The geneticist revealed on Wednesday that another volunteer is pregnant as part of his research,

He Jiankui said he has submitted the study, which he claimed was self-funded, to a scientific journal for review but did not name the publication. He dismissed concerns about the research being conducted in secrecy, explaining that he had engaged with the scientific community in the past three years. The scientist said gene editing would help protect the twin girls from infection from HIV, the virus that causes AIDS.

He, however, apologised for the result being leaked unexpectedly. The conference moderator, Robin Lovell-Badge, said the summit’s organisers were unaware of the story until it broke. The CRISPR-Cas9 technology allows scientists to essentially cut and paste DNA, potentially genetic fixes for disease. However, there are concerns about safety and ethics.

On Monday, China’s National Health Commission said that it was investigating the matter. “We have to be responsible for the people’s health and will act on this according to the law,” the commission said in a statement, Reuters reported.

The Chinese Society for Cell Biology on Tuesday strongly condemned the application of gene editing to human embryos for reproductive purposes and said that it was against the country’s laws and medical ethics. More than 100 scientists, most of them in China, also criticised He Jiankui. They wrote an open letter on Tuesday saying the use of CRISPR-Cas9 to edit human embryo genes was dangerous and unjustified. “Pandora’s box has been opened,” they said.