The Patna zoo was closed on Tuesday after strains of avian influenza virus were found in six dead peacocks, PTI reported. The Sanjay Gandhi Biological Park, Patna, will be shut until further orders, forest officials said.

“We are not sure how the peacocks contracted the virus,” Bihar Principal Chief Conservator of Forests DK Shukla said. “Birds from outside tend to fly inside the sprawling campus. That could be a possible reason but that is a matter of investigation.”

Samples of the dead peacocks were sent to Bhopal and Kolkata for tests, Shukla said. The laboratories confirmed the presence of the H5N1 virus.

“Although not fatal, the virus spreads rapidly and the decision to temporarily shut down the zoo was taken to minimise the possibility of catching the infection,” Shukla added. “The zoo is being thoroughly sanitised and experts would examine the campus after five days. Only after it is certified that it was safe for people, would the zoo be again thrown open for visitors.”

Most avian influenza viruses do not infect humans. However, sub-types, such as H5N1 and H7N9 have been known to cause serious infections in humans. The virus is transmitted to humans only when there is close contact with infected birds or heavily contaminated environments.