LONDON (AP) — DNA and other confidential health data from 500,000 people who volunteered for a massive U.K. health study were offered for sale online in China following a data breach this week, the British government said Thursday.

The information from the U.K. Biobank database was found listed for sale on the website Alibaba, but names, addresses, contact details or telephone numbers were not included, the technology minister, Ian Murray, told lawmakers.

Murray said he could not give a complete guarantee that nobody could be identified as the data could include gender, age, month and year of birth, socioeconomic status, lifestyle habits, and measures from biological samples.

Murray said the information had been legitimately downloaded by three research institutions in China, who have now had access revoked. Monday’s breach was an “unacceptable abuse” of the data and the government is working to figure out how it happened, Murray said.

Those who agreed to make all their health-related data available for research were 40 to 69 when they joined the study from 2006-2010. The participants provide detailed information about their lifestyle via online questionnaires, and consented to providing data from their health records and related information Some also provide body scans with medical imaging equipment, provide additional blood, urine and saliva samples, wear physical activity monitors or heart health monitors.

All the information is used to assess how diseases develop.

Murray said the breach was an “unacceptable abuse of the U.K. Biobank charity’s data and abuse of the trust that participants readily expect when sharing the data for research purposes.”

Thanking the Chinese government for its cooperation, Murray said no purchases had been made and that the data has now been taken down.

U.K. Biobank is the world’s most comprehensive dataset of biological, health and lifestyle information, and has been used to achieve improvements in detection and treatment of dementia, cancers and Parkinson’s. It can be used by scientists around the world for research that is deemed to be in the public interest. Data from it has been cited in more than 18,000 peer-reviewed scientific papers, including on major causes of ill-health.

Apologizing to participants, U.K. Biobank chief executive Rory Collins said the charity had temporarily closed access to the research platform and that additional security measures will be put in place.

Elena Simperl, a professor in the department of informatics at King’s College London, said the costs of maintaining infrastructure for flagship data stewardship projects like that of U.K. Biobank are treated as an “afterthought.”

“The U.K. has built something remarkable, but we need to keep investing in keeping it safe,” she said.