When the occupants of a flat in Pasir Ris Drive 3 refused to open the door despite repeated warnings, Central Narcotics Bureau (CNB) officers forced their way in.

They found a 24-year-old Singaporean woman hiding inside a cupboard, and another 29-year-old woman, also Singaporean, in the flat.

The officers recovered about 194g of heroin, 154g of Ice or methamphetamine, 101 Ecstasy tablets, 22 Erimin-5 tablets and two digital weighing scales. They also found four parangs and a baton.

It was a dramatic conclusion to an operation which took place on Monday. In total, CNB arrested five suspected drug offenders and recovered more than $74,000 worth of drugs. The haul included about 427g of heroin, 409g of Ice, and the 101 Ecstasy tablets and 22 Erimin-5 tablets.

That amount of heroin is enough to feed the addiction of about 203 abusers for a week, while the Ice haul can feed the addiction of about 234 abusers for the same amount of time, CNB said in a statement.

CNB officers had been observing a 27-year-old Singaporean man in a white car parked at a petrol kiosk in Pasir Ris Drive 1, and his 28-year-old Singaporean male passenger, before the raid on the flat. The officers moved in quickly when a third suspect approached the car on his Malaysian-registered motorcycle.

From the car, they recovered about 227g of heroin and 253g of Ice. CNB also found about 6g of heroin, a small amount of Ice, drug paraphernalia and $3,500 in cash on the motorcycle, and recovered $4,000 from the third suspect, a 28-year-old Malaysian man.

Following the arrests, CNB officers moved in on the home of the 27-year-old Singaporean man, where they arrested the two female suspects.

Investigations into the drug activities of all the suspects are ongoing.