Dozens of provincial officials and hospital staff attempted to cover up a lead poisoning case that made hundreds of children sick in north-west China and sparked widespread outrage, an official investigation has found.

The officials tampered with the blood tests of students who were poisoned at Peixin Kindergarten in Tianshui city, Gansu provincial authorities said in a report on Sunday.

City officials also accepted bribes from an investor in Peixin while neglecting food safety inspections across several pre-schools, the report said.

In an attempt to attract more students, Peixin chefs had used inedible paint to "enhance the look" of its meals, the report said.

Food samples were later found to contain lead 2,000 times in excess of the national safety limit.

Eight people were initially detained for their involvement in producing the toxic snacks. Six of them - including the kindergarten's principal, cooks, and an investor - have been arrested, according to the report.

Ten other officials will face "formal accounting procedures" while another 17 people are under disciplinary investigation.

Authorities revealed on 8 July that 235 children from the privately-owned kindergarten were being treated in hospital for lead poisoning after eating steamed red date cakes and sausage corn buns.

As of Sunday, 234 of them have been discharged.

The Gansu Provincial Centre for Disease Control and Prevention was ordered to test 267 students and staff at Peixin after some showed symptoms earlier this month, but officials "did not take the work seriously".

The person in charge of the tests "seriously violated operating procedures, which distorted the results", according to the report.

The report named several people under investigation and set out lead concentrations of various food samples, among other details.

It also accused staff at the Tianshui No. 2 People's Hospital of "serious dereliction of duty" and described the institution's management of the case as "chaotic".

The Chinese internet paid keen attention to the report, with some commending what they see as transparent disclosure and others asking for perpetrators in this case to be held accountable.

In contrast to its chiding of provincial and city-level officials, the report said there was "quick response" from the central government, which convened an expert panel "at the earliest opportunity" to review any gaps in procedures.

On Monday, China published a set of national guidelines for the provision of meals on campuses. Among other things, it mandates that every new batch of food must be tested, and that rice, flour and cooking oil must be bought at centralised procurement points.

Authorities in Tianshui have also announced that children suffering from lead poisoning can receive free treatment at designated hospitals, and legal assistance will be made available to affected families.

Peixin will be temporarily managed by a state-owned kindergarten.