SAN FRANCISCO -- San Francisco health officials have posted warnings in the city's Marina District after a bat found wrapped in a towel on a street tested positive for rabies.

Officials said the bat was found alive but ill Saturday evening near the intersection of Beach Street, Mallorca Way and Cervantes Boulevard. Apparently it had been captured in a local home.

A resident called authorities and the bat was picked up by animal control. As a standard precaution it was tested for rabies and that test came back positive.

Yellow notices have been placed on utility poles in the neighborhood warning residents of the danger and asking anyone who came in contact with the bat to immediately call health officials at 415-554-2830, 24 hours a day, 7 days a week.

Vaccinations are available to prevent rabies, which can cause coma and death in humans. However, once symptoms begin -- which can take anywhere from nine days to more than a year -- there is no effective treatment.

Health officials said as many five rabid bats are found annually in the city.