Fourteen children undergoing blood transfusions have tested positive for infections such as HIV, Hepatitis B and Hepatitis C at a hospital in Uttar Pradesh’s Kanpur, the Hindustan Times reported on Monday.

The children, who underwent transfusions at private and district hospitals for the thalassemia blood disorder they were already suffering from, are from different parts of the state, including Kanpur city, Etawah and Kannauj.

The children are between 6 years and 16 years.

Arun Arya, the head of the paediatrics department at the Lala Lajpat Rai hospital in Kanpur, told the Hindustan Times that seven of these children tested positive for Hepatitis B, five for Hepatitis C and two for HIV.

While the exact cause is unclear, Arya said the blood transfusion may have happened during the “window period”.

When blood is donated, it is tested to ensure that it is safe for use such as for transfusions. However, if tests are conducted only a short time after a virus has infected the donor, they may not be able to detect the pathogen. This time span is called the window period.

“This seems to be the case…” Arya told the newspaper. “The children are already battling a serious issue and are now at a greater health risk.”

District officials will now try to identify the cause of the infections under the Viral Hepatitis Control Programme, an official from the state’s National Health Mission said.