A British hospital on Thursday was conducting an internal investigation after a 5-year-old boy died of multiple organ failure as a result of the chicken pox, London’s Daily Mail reported.

"I strongly believe that if [the hospital] had just checked him over properly, he would be alive today," said the boy's father, Ricardo Nunes, whose son, Fabio, died in March.

Nunes, who spoke about the situation publicly Thursday for the first time, took Fabio to East Surrey Hospital in Redhill, England, on Feb. 14 but said the hospital told him his son was OK even though Fabio was unable to walk or talk and was barely conscious.

Four days later, when Nunes took Fabio back to the hospital, medical staff told him the boy was suffering from a severe reaction to the chicken pox and had only hours to live.

We are "taking this extremely seriously," said a spokesman for Surrey & Sussex Healthcare National Health Service Trust. "We are carrying out a full and thorough investigation into the circumstances surrounding Fabio’s care and condition."

Click here to see a picture of Fabio and to read the full story from the Daily Mail.