Ranchi: The Centre has sent an alert to the Jharkhand government to remain cautious about a possible poultry infection, after a mysterious bird flu-like virus is believed to have killed between 500 and 1,000 crows in Jamshedpur, Bokaro and parts of Hazaribagh. Though an official intimation from the Union animal husbandry department is still to reach the state, a study on the crow deaths conducted at the animal disease laboratory in Bhopal found a virus resembling that of bird flu.