A total of five misconduct notices have been served after a man died after being released from police custody.
It is part of a probe into police contact with 24-year-old Mohamud Mohammed Hassan from Cardiff.
Mr Hassan was arrested at his home on suspicion of breach of the peace but was released without charge the next day, 9 January, and died that night.
South Wales Police said: "The force continues to fully co-operate with the investigation."
The Independent Office for Police Conduct (IOPC) said notices had been served on a further three South Wales Police officers and a custody officer after an initial notice was served on one officer in February.
That officer has also received an updated notice.
Three of the notices relate to when Mr Hassan was in custody at Cardiff Bay police station, and two concern the actions of officers who attended the Newport Road address on the evening of Mr Hassan's arrest.
The IOPC said it had served:
- A notice at gross misconduct level on a police officer that they may have breached police professional standards of duties and responsibilities, and honesty and integrity.
- A notice at misconduct level on a police officer concerning their use of force while escorting Mr Hassan shortly after he arrived at the custody suite.
- A notice at misconduct level on a custody detention officer that they may have breached police professional standards of duties and responsibilities concerning the adequacy of welfare checks carried out.
In terms of the evening of Mr Hassan's arrest for an alleged breach of the peace, the IOPC said it had served notices at misconduct level on two police officers concerning their decision-making on use of force on Mr Hassan when at the property.
"We are considering whether the use of force was necessary and proportionate in the circumstances," the body said.
The IOPC said service of a misconduct notice did not necessarily mean an officer had committed any wrongdoing, but was to notify an officer that their conduct was being investigated.
If an officer is found to have breached professional standards at gross misconduct level they can be dismissed, and at misconduct level they can receive a written warning.
IOPC director for Wales, Catrin Evans, said: "We have updated Mr Hassan's family and South Wales Police about the further misconduct notices.
"We keep misconduct notices under review during the course of an investigation.
"As I have urged before, an investigation like this does take time and we would ask people to be patient while the investigation runs its course."
Hundreds of people joined a protest march through Cardiff after Mr Hassan's death.
A spokeswoman for South Wales Police said it the force provided the IOPC with information and material, including CCTV footage and body-worn video.
She added: "We acknowledge the impact Mr Hassan's death has had on his family, friends and the wider community. Our thoughts and condolences continue to be with them."