Black patches of oil washed up on a stretch of East Coast Park yesterday, leaving parts of both the shoreline and waters covered with the substance.

When The Straits Times arrived at the stretch of affected shoreline near Carpark F2, there was a greasy smell in the air.

Contractors from the National Environment Agency (NEA) were spotted near the affected beach area - which NEA said was about 400m long.

Mr Daniel Tong, 43, assistant operations director of De-Prospero, which runs the Central Thai restaurant nearby, said he first noticed the smell of "raw oil" at around 5.30pm yesterday. "I was walking past when I saw the oil around the break of the waves," he said.

He added that business at the restaurant, which has an alfresco dining area and is located about 50m from the affected stretch, was slightly affected as patrons were bothered by the smell.

"Hopefully this can be taken care of soon because it's not good for the environment," said Mr Tong.

Business adviser Guo Yanhuai, in his 50s, was jogging along the track at East Coast Park when he, too, noticed the smell. He discovered the black patches of oil when he headed towards the beach to investigate.

NEA said that clean-up operations will start today "at first light".

"Members of the public are advised to exercise caution when visiting this section of the beach and to avoid the affected stretches where cleaning operations are on-going. NEA is also closely monitoring the quality of the seawater," said the NEA spokesman.

The Maritime and Port Authority (MPA) said it was alerted at 5.42pm to the incident. It said in a statement: "MPA has deployed patrol boats with oil dispersants along the area. There has been no sighting of oil found at sea. We are investigating the situation."

•Additional reporting by Lim Yao Hui