Drug enforcement and police officers rescued a one-year-old boy from suspected drug traffickers after his caregiver had left him in their care.

Central Narcotics Bureau (CNB) officers learnt about the boy after they picked up his caregiver, a 33-year-old Singaporean woman, around Kinta Road near Farrer Park MRT station on Monday.

She was suspected of trafficking drugs after being found carrying a bag containing about 195g of heroin and 27g of methamphetamine, or Ice. Another 20 Ecstasy tablets and a small amount of heroin and Ice were found near Roberts Lane.

Officers suspected she may have a baby as her phone messages made references to one. After initially denying it, she later revealed she was the caregiver of a one-year-old boy.

In an operation the next day, CNB and police officers nabbed a 51-year-old man in a hotel room near Joo Chiat. He was spotted with the boy before his arrest for suspected drug trafficking.

Two women, aged 38 and 41, were also arrested for drug-related offences, a CNB statement said.

A second man, who had booked the hotel room, was arrested in his home in Rivervale Drive. The 34-year-old is being investigated for drug trafficking offences.

The boy is now in the care of the Ministry of Social and Family Development's Child Protective Service, a CNB spokesman said, adding that his birth was not registered.

Efforts are "currently underway to locate the biological mother of the toddler, who is also wanted for drug offences", he added.

About 640g of heroin - enough to feed the addiction of about 305 abusers for a week - was seized when officers raided the hotel room on Tuesday, CNB said.

Mr Sng Chern Hong, CNB's spokesman, said the case "clearly highlights the adverse consequences of drugs".

"It was fortunate that our officers were successful in locating the toddler and prevented further harm from being caused to him," he added.

The suspects are all Singaporeans. Investigations are ongoing.