A recently implemented fingerprint-scanning system has in the last month led to some travellers trying to enter Singapore using false identities being turned away.

"Since we implemented the BioScreen system, we have detected some passengers trying to enter Singapore with different passports," Senior Minister of State for Home Affairs Desmond Lee told reporters at Changi Airport yesterday.

He was visiting a checkpoint at Terminal 3 for an update on the system's implementation. It will eventually be used to verify the identities of all travellers passing through manned counters at the airport before they are granted entry into or allowed to depart from Singapore.

From April 20 to May 19, over half a million people were cleared through the system at land and sea checkpoints and at Changi Airport, the Immigration and Checkpoints Authority (ICA) said in a statement. During this period, it also detected individuals who had previous offences, such as immigration offences.

No other details were given.

Someone going through the system would have to place both thumbs on a device at the immigration counter. During Mr Lee's visit, it took passengers 10 to 15 seconds to have their prints scanned.

"Using technology allows us as far as possible to enhance security while ensuring minimum hassle to passengers," Mr Lee said, noting that the threat of a terrorist attack has been at its highest in recent years. He advised people travelling during the busy June holidays to set aside more time for clearing immigration.

The scanning system has progressively been rolled out across land and sea checkpoints from April 20, beginning with manned counters in passenger halls for the Woodlands and Tuas land checkpoints.

It has been operating in Changi Airport since April 27, but the ICA declined to say when the system will be fully up and running at all manned counters.

ICA checkpoint inspector Chua Swee Noi, who works at Changi Airport, said some travellers are a bit impatient at having to wait longer to be processed. They, however, generally accept the need for greater security.

ICA inspector Mohamed Ashik, who also works at Changi Airport, said officers are in place to guide travellers on the proper way to place their thumbs on the scanner to expedite the process. He said the ICA would put more officers on duty during the school holidays, if needed.