Indigenous readers are advised this report contains the name and image of a person who has died, used with the permission of their family.

The family of Indigenous man Lynton Ryan is searching for answers after his death in custody.

On April 2, Mr Ryan was found unresponsive in his cell in Eastern Goldfields Regional Prison in Kalgoorlie-Boulder in WA.

His mother, Lynette Smith, told the ABC she "just broke down" after being told of his death the following day.

"I was in a deep shock," she said.

Mr Ryan, who was born in Port Pirie, South Australia, was 31 at the time of his death.

At the time, the WA Department of Justice said preliminary reports indicated there were no suspicious circumstances.

For all deaths in custody a coronial inquest is mandatory.

Ms Smith believes Lynton, her youngest son, took his own life, she and her eldest son Shannon Smith are still waiting for answers.

Speaking to the ABC, Mr Smith asked: "What happened in the last two hours? What is the exact cause of the death?"

He also wanted to know how his younger brother "fell through the cracks in the system" to be found "dead in his cell".

"I looked at that cell," he said, after visiting the prison for a cultural smoking ceremony.

"It's a terrible place to die.'

Mr Smith told the ABC his younger brother had recently been living in Kalgoorlie and was only in prison for three days prior to his death.

It is understood he had been taken into custody for disorderly behaviour in town.

Mr Smith said he feared it could take years before they knew exactly how he died.

"They have CCTV — why do we have to wait for so long?" he said.

"Our mother's health is not good. She won't be around forever."

Close to 600 Indigenous people have died in custody since the Royal Commission into Aboriginal Deaths in Custody brought down its findings and more than 300 recommendations in 1991, many of which remain unimplemented despite the consistent campaigns by justice experts and other Indigenous leaders calling for full implementation.