Police in Greymouth are looking for a man who allegedly sexually assaulted a young woman early on Wednesday morning.
They say the man is dark-skinned, up to 183 centimetres (six feet) tall, has dark hair and facial hair, and is in his 20s.
He was wearing white gumboots, dark jeans and a hat.
Anyone who may have witnessed the attack, or who knows the man, should contact police.