SINGAPORE - Investigations into the death of a Singapore Civil Defence Force full-time national serviceman (SCDF) have widened to more officers, with four having their promotions withheld.

Two SCDF regular personnel, who were arrested on Monday (May 14) in relation to the death of Corporal Kok Yuen Chin, will also be suspended from service on half-pay pending the outcome of police investigations. The duo - a Warrant Officer 1 and a Staff Sergeant - were Cpl Kok's colleagues who worked in the same shift duty at the station.

The four, whose promotions are being withheld, were supposed to move up the ranks on June 1, according to a statement from the Ministry of Home Affairs on Wednesday (May 16) that provided updates on Cpl Kok's case.

Cpl Kok, 22, died after he was found unconscious inside a pump well at Tuas View Fire Station on Sunday night.

The Singapore PR had been celebrating his impending operationally ready date (ORD) with his squad mates, which involved him getting into the pump well as part of ragging activities. He would have completed his service in two days.

In its statement, the MHA added that a Board of Inquiry (BOI), convened to look into his death and to make recommendations to prevent similar incidents, will be chaired by a senior director from the Ministry of Trade and Industry.

The BOI will include members who are not from the MHA or the SCDF, and will submit its report to the Minister of Home Affairs.

Separately, the state coroner may call for an inquiry into the death. The Attorney-General's Chambers is also reviewing the case with a view to criminal proceedings.

The police had arrested the two SCDF regular personnel based on preliminary investigations into what had happened, including how Cpl Kok fell into the pump well, and whether anyone is criminally responsible.

SCDF Commissioner Eric Yap, in a strongly-worded letter on Wednesday to all officers, said unit commanders would be accountable and responsible for any unauthorised initiation or ragging activities by any personnel under their charge.

He added that he had personally briefed all commanders on Tuesday and underlined the importance of command responsibility.

"As an organisation, and as individuals, I am sure every one of us is grieved and horrified by this unfortunate incident. Each day, we put our lives at risk to protect and save lives and property. We pride ourselves on being the Life Saving Force," he said.

"But amongst us, there may be some who flout the rules, or turn a blind eye to unauthorised initiation or ragging activities being carried out by officers who clearly do not embrace our core values.

"Let me be clear about this - those of us who are aware of, or have seen such acts being carried out but yet do not stop or report these acts, also bear responsibility. We cannot condone or allow any wrongdoing."

Stressing that commanders are entrusted with the responsibility to look after the men and women who risk their lives every day, the commissioner said: "There must be zero tolerance for any officer who contravenes the rules, and we must take all necessary measures to eradicate such activities."

He added that the incident had damaged the credibility of the SCDF, and there was a need to regain the trust of the public, families of NSFs and SCDF officers.

He pointed out that Cpl Kok would have completed his full-time national service on Wednesday and left the SCDF with a strong testimonial reflecting his good performance and outstanding conduct.

"Even as we mourn the loss of one of our own, we owe it to Cpl Kok to ensure that this must never happen again," said the commissioner.