India, Aug. 31 -- A total of 12 birds have died at the Delhi Zoo since Wednesday last week, officials said on Sunday, adding that four birds - three painted storks and a black-headed ibis - are currently unwell and being monitored.

HT had reported on Sunday that samples of four of the dead birds have been found positive for avian influenza (bird flu) and the zoo premises was therefore temporarily shut from Saturday till further notice.

"Intensive surveillance and strict bio-security measures have been strengthened to prevent spread and communication of the avian influenza disease among animals, birds and staff at the National Zoological Park. Surveillance teams are surveying the entire premises twice a day. Intensive cleaning and disinf...