Health officials were investigating whether a 79-year-old woman who died on Saturday in Queens was a fourth victim of the brain-swelling viral infection named after the city where it first appeared in 1933.
The number of confirmed cases of St Louis Encephalitis (SLE) in the first recorded outbreak of the disease in New York City remained at nine, including three elderly people who died, officials said. Tests were done on 89 people suspected of being infected.
The outbreak, traced to birds that carried the virus from southern regions and transmitted it to the local mosquito population, became apparent to health officials on 2 September.
Meanwhile, doctors in Albany, New York state, were investigating whether a 31-year-old woman who died on Sunday morning was a victim of SLE. Preliminary blood tests showed she was not.
Health workers used trucks to spray the insecticide, malathion, over the 843 acres (340 hectares) of Central Park during a seven-hour period starting late on Sunday night.
Large areas of the boroughs of Staten Island and Queens were also sprayed on Sunday night. Aerial spraying began last week in residential areas. Mayor Rudolf Giuliani ordered the spraying be spread to cover the city's five boroughs after the outbreak spread beyond Queens.Reuse content