A Vietnamese woman was found with more than four kilograms of a substance suspected to be the drug 'Ice' when she landed at Changi Airport on Saturday morning.

Officers from the Immigration and Checkpoints Authority and the Central Narcotics Bureau found two slabs of the crystallised substance wrapped in aluminium foil in the 47-year-old's luggage.

They estimate the haul to be worth around $630,000. If convicted, the woman may face the death penalty.

Preliminary investigations suggest that the drug was intended to be re-exported and not for the Singapore market, said an ICA spokesman.

The ICA reiterated that border security was "critical" to Singapore, and stated that it would continue checks at all checkpoints to prevent smuggling.

"The same methods of concealment used by contraband smugglers may be used by terrorists to smuggle arms and explosives to carry out attacks in Singapore," said the spokesman.