Provincial health officials and hospital workers tampered with blood tests in a case of lead poisoning that sickened more than 250 kindergartners in western China, Chinese authorities said, in a rare acknowledgment of a high-level hush-up of a public scandal.

The authorities in Gansu Province also accused education officials in the city of Tianshui of turning a blind eye to the fact that the kindergarten in question was unlicensed and accepted unauthorized gifts from an investor in the school. Food safety inspections at the school were perfunctory, according to an official report released on Sunday by a special investigative team convened by the Gansu provincial Communist Party committee and government.

Even before the release of the report, the lead poisoning scandal had dominated public discussion for weeks in China, where food safety has been a long-running concern.

The poisoning stemmed from powdered pigments that the school staff had used as food coloring, the report said. Some of the pigments, which were marked as inedible on its packaging, consisted of more than 20 percent lead; lead levels in the food the children were given exceeded the national food safety standard by 2,000 times.

But the investigation results further fueled public outrage at the official misconduct on multiple levels. Some parents at the preschool had already said they suspected a cover-up, even taking their children to other provinces for testing. Now their fears were confirmed.

One child was found to have elevated levels of lead six times over the course of half a year, starting in November 2024, without the hospital, Tianshui No. 2 People’s Hospital, issuing any alert, the report said. The hospital also modified the records of two more children who showed elevated lead levels, reporting a blood lead level nearly seven times lower than the actual result for one of them.