Chandigarh's Sukhna Lake was cordoned off early Thursday after a sample from a dead duck tested positive for the H5N1 (avian or bird flu) virus.
Police and paramilitary personnel with masks on their faces were stationed at the lake complex since early Thursday to cordon off the entire area.
Scores of morning walkers who throng to the lake every day and other visitors were kept away from the lake complex.
Police officials at the lake told IANS that the complex would remain out of bounds for all visitors for at least two to three days.
Wildlife and animal husbandry department officials are likely to start culling of the ducks and geese at the lake to curb an outbreak of bird flu in the city.
Over 30 ducks and geese at the lake had died under mysterious circumstances in recent days. The Sukhna lake has nearly 250 ducks and geese which are a star attraction for visitors.
The presence of the H5N1 virus was confirmed in a sample from one dead duck by the Bhopal-based National Institute of High Security Animal Diseases (NIHSAD) Wednesday.
Ducks and geese have been dying for the past 10 days and officials initially thought the deaths could be due to food poisoning or over-feeding.
"At present, there is no assessment regarding any outbreak of bird flu in Chandigarh. The situation is, however, being very closely monitored," a spokesman of the Chandigarh Administration said.
While claiming that there was "no alarm or alert issued for the general public", the authorities ordered the lake area where the ducks and geese reside to be fenced.
"The movement of the ducks and geese has been restricted," the spokesman said.
"The public are requested not to panic and cooperate with the administration," the spokesman added.
The Sukhna Lake is in an upscale, high-security area of Chandigarh - the joint capital of Punjab and Haryana and a union territory.
The residences of the Haryana and Punjab Governors, senior officers and other influential people are located close to the lake complex.