A person reported seeing a bear at about 11 p.m. in the area of Burlington Drive, according to Petaluma police.
Soon afterward, a second person reported seeing the bear in the creek in the area of East Washington Street and Maria Drive, according to police.
The bear was apparently traveling east near the Washington Creek and toward Sonoma Mountain, police said.
Two other sighting were reported at the corner of East Washington Street and Sonoma Mountain Parkway, according to police.
The bear was not found after a long search by Petaluma police, assisted by a California Highway Patrol helicopter.
The animal is described as a black bear that weighs about 200 pounds. Anyone that sees the bear should not approach it, and should contact authorities, police said.