A toddler in Guizhou, China, has contracted the human immunodeficiency virus (HIV), possibly while undergoing treatment in hospital.

Chinese Communist Party newspaper Beijing Youth Daily said on Saturday (July 28) that China's National Health Commission, the country's highest authority on health issues, has commenced a 10-day investigation into the matter.

In an open letter, parents of two-year-old Xiaotian (not his real name) said that he had been rushed to the Guiyang Maternal and Child Health Hospital in October last year after he accidentally breathed in a chunk of apple. He was tested negative for HIV when he was admitted.

The letter also mentioned that both parents were tested to be HIV-negative.

After his symptoms worsened, the child was transferred to to the Children's Hospital of Chongqing Medical University in December that year, China Daily reported on Friday. He was then found to be HIV-positive.

Xiaotian was tested twice in June this year at different hospitals, and was confirmed both times to have HIV.

On Friday, the Guiyang Municipal Health and Family Planning Commission said in a statement that it received a complaint and had started a multi-department investigation, reported state news agency Xinhua on Saturday.

The agency immediately conducted blood tests on 33 medical personnel that had come into contact with the boy, as well as on blood samples. No abnormalities were found.