Officials are trying to track the source of an oil slick that left sludge on Repulse Bay beach yesterday.
The Marine Department says preliminary investigations show the oil did not originate from land, but so far officers have drawn a blank. However, they say it is not connected to an oil spill off Tuen Mun on Sunday.
The beach on Hong Kong Island, which is popular with both locals and tourists, was closed for a clean-up by the Leisure and Cultural Services Department.
It was not known last night if it would be reopened today.
The department was alerted at about 9am yesterday to a large patch of oil that was floating off Round Island, which is about two kilometres south of the beach.
The oil - which marine officials described as a 'rainbow-coloured oil sheen' - then gradually began drifting towards Repulse Bay. It started to hit the shoreline at about 12.40pm.
A thick layer of oil was also spotted in a corner of the sea just off the Kwun Yam shrine on the beach.