A great white shark sighting in the coastal waters of Australian city of Newcastle forced the closure of beaches for a sixth day on Thursday. The shark is nearly 16-foot long and was first spotted on Saturday.

The shark was last seen off Nobbys Beach on Wednesday afternoon, Newcastle City Council Aquatic Services Coordinator Peter Withers said, according to The Associated Press (AP). Authorities reportedly said that the shark is "of a size that has not been seen before around Newcastle."

The beaches have been closed for the public in the city, about 100 miles north of Sydney. Shark sightings are common in Australian beaches, but this was the first time it had remained in an area for such a long duration, Withers reportedly said.

A surfer had spotted a dead dolphin washed ashore at Burwood Beach. It is rumored that the dolphin may have been attacked by the shark.

"It was a full dolphin except there was a section of its tail missing. People hear about the great white but they still go out. This shows what can happen to someone,” the surfer told Sky News.

Authorities were patrolling the area on Thursday in search of the shark, Withers said, according to AP.