Marine and Ports officials have admitted they do not know exactly what the murky brown sludge seen on the water near the Ferry Terminal on Front Street last week was.

The mysterious murky brown sludge has been popping up at several other bays around the Island and Marine and Ports has received numerous calls about it from curious residents.

While unable to pinpoint a definite cause of the sludge, one official has a possible theory about where it could have come from.

The brown murk was spotted dockside along Albuoy's Point and extended along the dock to Front Street. A large deposit was seen off the bow of the Pacific Princess .

Marine & Ports mooring officer Ron Boys said he had also seen the sludge at the west end of the Island and said he believed it might have been caused by Casuarina seeds which have fallen into the water and broken up when sodden to create the brown murk.

"This is a natural phenomenon,'' he said.

Another alternative theory was that the sludge could have been coral spawn but Mr. Boys noted there was hardly any coral in the harbour so that solution could be ruled out.

Director of Marine & Ports Ron Ross said the sludge had been on the water for about a week and had been blown along the shores by the wind.

He said: "We have had winds to the east which could be why there is a build up along the shores.''