A Ministry of Defence (Mindef) defence executive assistant who was being detained at the Singapore Armed Forces (SAF) Detention Barracks suffered a cardiac arrest while taking a shower on Friday and was eventually pronounced dead on Monday night.

In a statement, Mindef said 54-year-old Sivaperumal Tanggayelu was detained to "assist in investigations", and had collapsed at about 6.49pm on Friday.

A medic immediately started resuscitation efforts on Mr Sivaperumal, who was unconscious and without pulse. He was then brought to the Tengah Air Base Medical Centre, where an SAF doctor assessed that he had suffered from a cardiac arrest.

Mr Sivaperumal was then brought to the National University Hospital's (NUH) emergency department at about 7.40pm, with resuscitation efforts continuing en route.

The executive assistant was resuscitated at 8.15 pm but remained in critical condition, a Mindef statement issued on Monday night said.

Mr Sivaperumal was pronounced dead at 8.49pm on Monday.

Prior to his detention, Mr Sivaperumal had been assessed to be medically fit for remand and the 54-year-old had not reported sick or complained of feeling unwell when he started his detention. He had also been excused from physical activities.

The statement said that the SAF is providing assistance to the family and is investigating the incident.