The Delhi Zoo lost all four of its monitor lizards after a staff member took them out of their enclosures during their hibernation period, PTI reported on Thursday. The incident took place on January 28 and the postmortem report said the lizards had “died of shock”.

Monitor lizards usually hibernate from November to March every year and they are not disturbed during this period. The reptiles are also do not need to be given food or water during this time. They undergo drastic temperature fluctuations if taken out of their hibernation period.

Disciplinary action was taken against the zoo ranger who had pulled the lizards out without seeking permission, curator Riyaz Khan said. Two reptiles had died on February 1 and 2. The remaining ones were kept under special care, but they were unable to recover and died on February 11 and 15, an unidentified official told The Times of India.

A detailed report regarding the incident was being prepared by the zoo authority, Khan said.

The zoo had reopened in January after it had to shut down in October 2016 after as many as 14 birds had died from avian influenza. A Cape buffalo had died in the zoo last week as it was ill and was unable to recover from tuberculosis, The Times of India added.