The Central Narcotics Bureau (CNB) on Monday evening seized more than $59,000 worth of drugs in an operation that led to the arrests of three men and a woman.

The 545g of heroin, 14g of "Ice" and "Ecstasy" tablets seized are estimated to be enough to sustain 260 abusers for a week, said CNB in a statement on Tuesday.

At about 6pm on Monday, CNB officers spotted the first suspect, a 36-year-old Malaysian man, arriving on his motorcycle at a carpark in the vicinity of Sims Drive. He was seen placing a plastic bag on the handle bars of his vehicle.

About an hour later, the officers spotted a panel van driving into the same carpark. The Malaysian man approached the van and took an envelope from someone who was at the back of the van. He then returned to his motorcycle, took the plastic bag, and walked back to hand it to another suspect in the van. Both groups parted ways shortly after.

CNB officers subsequently moved in to arrest the man, as well as the three other Singaporean suspects - two men aged 41 and 36, and a woman aged 32 - who were in the van. The drugs, along with a drug-smoking apparatus, were recovered from the van. Cash amounting to $4,400 was also recovered from the Malaysian suspect.

Investigations into the suspects' drug trafficking activities are ongoing.