Mystery surrounds the source of an oil slick which was discovered in Hamilton Harbour yesterday.

A Harbour Radio spokesman said that the slick disappeared by itself and efforts by Marine Police to determine exactly where it came from were unsuccessful.

?It seemed to just creep over the dock area this afternoon.

?And it dispersed by itself,? said Harbour Radio.

But he noted that the slick itself was not necessarily a serious threat to the environment despite appearances.

?Because the water?s so still even a small quantity appears to be quite dramatic.?