The directorate of revenue intelligence (DRI) has sought the post-mortem reports of the 53 birds that died at the Alipore zoo hospital, where they were kept quarantined after being seized from smugglers in and around Calcutta this year.

Deepankar Aron, additional director-general of DRI’s Calcutta unit, wrote to zoo director Asis Samanta on Tuesday, asking him to share the post-mortem details.

Copies of Aron’s letter have been marked to the Central Zoo Authority and the Bengal forest department.

Metro had on Tuesday reported that 53 of the 153 birds quarantined at the zoo hospital after being seized by DRI had died between June 2 and October 30. The death count has prompted the agency to question the conditions in which birds are kept at the hospital.

Samanta said he had not received any letter till Tuesday evening. “Post-mortem was done after every single death. The causes of the deaths mentioned in the report sent on November 1 were ascertained after conducting a post-mortem,” he said.

The causes mentioned in the report, which was appended to a letter addressed to Aron informing him about the deaths, include “infighting injury”, “enteris” and “neurogenic shock”.

Aron wrote back to Samanta calling for an inquiry into the series of death and proper care for the rest of the menagerie. “The zoo authorities are yet to respond to that letter.... Now, comes this prod from Aron,” a DRI official said.

Asked whether the zoo would conduct any probe, Samanta said: “Three experienced doctors at the zoo had signed the report attached to my letter. I don’t think there is any need for a further probe”.

V.K. Yadav, member-secretary of the Bengal Zoo Authority, said the zoo was not to blame. “Most of these birds were kept in sacks, gunny bags or tiny cages (before they were seized) and crammed into a car boot or under the seat. Many such rescued birds die in transit. The rest are also extremely vulnerable.”