A man being held in Western Australia's Yongah Hill Immigration Detention Centre says he is an Indigenous Australian and not a visa overstayer or asylum seeker.

The Immigration Department has strongly rejected the claim, saying they have used fingerprint and facial recognition analysis and have found the man to be a Fijian national.

Eddie David, 39, has been held in the centre since Friday.

He said he was born on Murray Island in the Torres Strait, and his claim was backed up by a WA Aboriginal land council.

Mr David told the ABC he was sent to Yongah Hill, near Northam, 97 kilometres north-east of Perth, after being told his passport was fake.

He said he had been mistaken for someone else, possibly a Fijian man of a similar age.

"I'm not a refugee and I'm not an immigrant," Mr David said from Yongah Hill.

"I am Aboriginal, I am an Australian citizen, born and bred of this land.

"I shouldn't be in this detention centre. If it was a fraud, they should have put me in the cell, in the lock-up, in the jail, not a detention centre."

The Department of Immigration and Border Patrol is adamant Mr David is not Australian.

"The department detained an individual claiming to be an Australian citizen, following a thorough investigation by which the department was fully satisfied that he is an unlawful non-citizen," it said in a statement.

"As part of the investigation, the department used fingerprint analysis and facial recognition comparisons."

It said the man who was detained was a Fijian national claiming to be an Australian citizen.

"The department also contacted the Local Aboriginal Council, who did not affirm his claims to be Aboriginal," the statement said.

Land council in no doubt about man's Aboriginality

However, the South West Aboriginal Land and Sea Council said its cultural advisor Kevin Fitzgerald signed a document affirming Mr David's Aboriginality when he applied for a passport.

Council community development officer Michelle Nelson-Cox also met Mr David and is convinced he is Aboriginal.

Michelle Nelson-Cox from the South West Aboriginal Land and Sea Council is convinced Mr David is Aboriginal. ( ABC News: Robert Koenig-Luck )

She said it was a major concern he was detained at Yongah Hill.

"We wouldn't be so optimistic to sign off on any documentation [if] we thought there was some doubt around his origins," Ms Nelson-Cox said.

"We were satisfied that he met all the criteria, and all the processes and protocols around sustaining that identity."

Ms Nelson-Cox said Mr David displayed knowledge of Aboriginal cultural protocols and knowledge about a mission in South Australia he claimed to have spent time at.

"The knowledge around this individual's upbringing and around his physique and some of the men's business that they discussed," she said.

"He was accepted on the grounds that he met the cultural values and cultural protocols."

Mr David said he had spent many years living on the streets, homeless and alcoholic in NSW and elsewhere, and had come to Western Australia several years ago.

He had wanted to access Centrelink benefits but was told he did not have sufficient identity papers.

He said he applied for a passport with the help of the South West Aboriginal Land and Sea Council, which he said he received in March.

But when he took it to Centrelink, they told him it was fake.

Passport dispute 'led to detention'

He said immigration officers then came looking for him through his part-time employer, bricklayer Daryl Rogers.

Mr David decided to go to the immigration office on Friday, where he said he was detained and sent to Yongah Hill.

Mr Rogers is sure Mr David is Indigenous.

"I worked with Eddie over the last 12-18 months," Mr Rogers said.

"He is Aboriginal. I think it's a mistaken identity."

Mr Rogers had spoken to immigration officers.

"I got a phone call from immigration on speaker phone saying, 'We've got Eddie David here. We think he's a Fijian. They said some name, which I don't know."

Human rights lawyer George Newhouse, who is representing Mr David, said he had sent letters to the Australian Government demanding his client be released.

"He has provided information to the Department of Immigration and yet they continue to detain him," he said.

"This is a very serious matter. It's not since the cases of Cornelia Rau and Vivian Solon that we've heard of an Australian being wrongfully detained and the Government needs to clear this issue up as a matter of urgency."

Mr David was at a loss to understand what was happening to him.

"But these detainees are helping me," Mr David said.

"They're shocked that there's an Aboriginal Australian in a detention centre.

"They say, 'This is your land, you should be out there, not in here'. It's a mistaken identity, I think it's just a facial mistaken of identity."

Australian permanent resident Cornelia Rau was mistaken for a visa overstayer and unlawfully detained in immigration detention for 10 months between 2004 and 2005.

Vivian Alvarez Solon, also an Australian, was wrongfully deported to the Philippines in 2001.