The sight of three men seemingly scooping shellfish at Sungei Buloh Wetland Reserve stunned a nature guide who was visiting the place over the weekend.

Mr Ben Lee, who works full time at Nature Trekker, swiftly informed the National Parks Board (NParks).

An officer arrived and confiscated plastic bags containing the molluscs from the trio.

Mr Lee, 54, a frequent visitor to the wetlands, told The Straits Times that he saw three men digging and scooping shellfish into large plastic bags at around 5.20pm on Sunday.

They did so for about 30 minutes.

One of the men looked to be in his late 40s, while the other two appeared to be in their 20s.

Mr Lee said the men were most likely digging up the molluscs for sale or personal consumption.

He added: "A nature reserve is a place for the preservation and protection of wildlife, and such illegal activities should not be allowed to happen."

NParks acting group director for conservation Adrian Loo said yesterday that the confiscated shellfish were returned to the mudflats.

NParks is investigating the incident, he added.

Dr Loo said signs are prominently displayed, informing people not to remove plants and animals from parks and nature reserves.

By doing so, they may disrupt the ecological balance, he added.

Under the Parks and Trees Act, those who remove, capture, cause disturbance or displacement of any plant or animal in public parks can be fined up to $5,000, and if they do so in national parks and nature reserves, the fine is up to $50,000.

NParks said 73 notices of offence have been issued so far this year for poaching in parks and nature reserves.

Of these, seven were for poaching at Sungei Buloh Wetland Reserve.

Most of them involved illegal fishing, or possessing or using fishing gear.