Algae-like bacteria has prompted a fishing ban and other restrictions at the Manasquan Reservoir.
Officials say cyanobacteria, which is bright-green in color, was detected in the water. It can produce harmful toxins that give people and animals gastrointestinal illnesses, rashes and other reactions.
Signs have been posted along the reservoir to warn parkgoers, but some fishermen say park rangers did not make them bring their boats in.
Officials say contact with the water should be avoided by both pets and humans.
The Manasquan Water Supply System says the bacteria poses no threat to drinking water because it's drawn from the other side and filters will remove trace amounts of bacteria.