Suspected gun parts have been found in a parcel sent by airmail.
The Immigration and Checkpoints Authority (ICA) said in a Facebook post on Friday that the items were uncovered when an officer noted anomalies in the scanned images of a parcel at the Airmail Transit Centre on June 29.
A total of 20 suspected gun parts were found in the parcel, which was declared as "merchandise".
Gun parts are regulated under Chapter 13 of the Arms and Explosives Act.
The case has been referred to the police, ICA said.
The ICA said it would continue to conduct security checks on passengers and vehicles to prevent smuggling attempts of undesirable persons, drugs, weapons, explosives or other contraband.
"The same methods of concealment used by smugglers may be used by terrorists to smuggle arms and explosives to carry out attacks in Singapore," it said.