NEW DELHI, Dec. 25 (Xinhua) -- Authorities in eastern Indian state of Bihar Tuesday closed a zoo for an indefinite period following the deaths of six peacocks inside it due to avian influenza, also known as bird flu, officials said.

The deaths took place at the zoo in Patna, the capital city of Bihar.

Officials said the deaths were caused due to H5N1 virus.

"The zoo had been closed following deaths of six peacocks between Dec. 16 and Dec. 24," R K Sinha, a senior official at Patna zoo said.

"The carcasses of peacocks have been sent to National Institute of High-Security Animal Diseases in Bhopal where it was confirmed that the birds died after being infected with H5N1 virus."

Senior officials said the process of immunization and disinfection has been initiated inside the zoo and it would be reopened after it is established that it has been completely freed from the virus.

According to officials, Patna's zoo attracts a huge crowd through out the year.

Forest department officials say it was not clear how the peacocks contracted the virus and have ordered an investigation into it.

According to WHO, avian influenza is an infectious viral disease of birds. Most avian influenza viruses do not infect humans. However, some, such as H5N1 and H7N9, have caused serious infections in people.