The personal contact details of more than 400 operationally ready national servicemen (NSmen) were sent to one another by mistake after a government-appointed vendor made a technical error.
The 427 men from the Singapore Armed Forces (SAF) and Home Team had redeemed credits for service-linked rewards - the National Service Excellence Award and Celebratory Gifts for Operationally Ready National Servicemen.
The company in charge of these gift redemptions, Option Gift, said the men received the personal details on Tuesday due to an "erroneous programme script". It apologised for the error.
The incident occurred when the erroneous script was used to send out confirmation e-mail to inform servicemen about their redemption details.
"The company has notified the Ministry of Defence (Mindef) and the Ministry of Home Affairs," Option Gift said in a statement yesterday evening.
"We have also informed all affected NSmen of the error."
The company added that this was an isolated incident and that redemption services for all servicemen - including the group of 427 - are not affected.
In a joint statement, both ministries said they were aware of the incident and are investigating. They have put in place measures to prevent a recurrence, they added.
In February last year, Mindef revealed that the personal details of 850 national servicemen and Mindef staff were stolen in a "targeted and carefully planned" cyber attack on the ministry's I-net system.
When this happened, Mindef disconnected the affected server from I-net, but allowed I-net to continue to provide Internet access.
It investigated the I-net system, as well as other systems used within Mindef and the SAF.
A month later, a batch of SAF recruits had their identity-card numbers and photos published online by mistake before the authorities realised the error and removed the information a day later.
The Basic Military Training Centre, which was responsible for the error, apologised for the mistake and reviewed its procedures to prevent it from recurring.
NSmen who have questions about the latest incident involving Option Gift can call the NS Call Centre on 1800-367-6767.