Police now believe the 9-month-old baby whose body washed ashore on the world famous Surfers Paradise beach early on Monday died across the border in New South Wales.

Her lifeless, naked body was found lying in the sand at the edge of the water on Surfers Paradise Beach in a tragic discovery by a passer-by in the middle of the night on Monday.

However, it's now understood post-mortem results show the little girl drowned and may have been placed in the water at Tweed Heads, with her body eventually washing up 30 kilometres north at Surfers Paradise.

It means NSW detectives will travel to Queensland today to seek the extradition of a 47-year-old man as part of the investigation into the death of the baby girl.

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It is anticipated he will return to NSW where he will be served with a warrant.

About 12.30am on Monday, Queensland Police were called to Staghorn Avenue and the Esplanade, Surfers Paradise, after the girl was found unresponsive.

She was assessed by paramedics, but died at the scene.

Divers have been scouring waters across south of the Gold Coast in the hope of turning up clues as to the death of the girl who was found washed up.

Specialist officers were seen entering Jack Evans Boat Harbour at Tweed Heads, NSW, on Tuesday. The child's family, who were homeless, had lived for a time in Kingscliff, just inside NSW.

Queensland Police said they will continue to assist their southern counterparts after establishing the death occurred south of Coolangatta.

Second baby death

Just a day after the 9-month-old girl's body was found, another — even younger — child has been found dead in suspicious circumstances in Queensland.

Police say a 35-year-old woman and 37-year-old man are assisting with inquiries following the death of a 4-month-old girl in Logan, south of Brisbane.

The infant was transported to the Queensland Children's Hospital on Tuesday afternoon in a critical condition, where she later passed away.

Detectives child protection unit and the homicide and child trauma squads are investigating.

Gold Coast reacts

On Tuesday, several Gold Coast residents said they tried months ago to get help for the baby girl whose family often slept in local parks from Tweed Heads to Surfers Paradise.

The baby's 47-year-old father and 23-year-old mother are in custody but have not been charged.

The father of the baby girl reportedly told police she was "possessed by demons", according to Seven News.

The tragic death has exposed a massive homelessness problem beneath the glitz of the city skyline and furious locals are asking how this could have happened.

At least two locals say they contacted police and other authorities about the family, which had been sleeping rough near the beach where the 9-month-old was found dead.

Local resident Erin Sorensen says she went to police two months ago to share her concerns about the baby, as well as a toddler who was also sleeping rough with the couple. "Clearly, I wasn't taken seriously," she wrote on Facebook.

"It was winter and the dunes were freezing every time the sun went down. I didn't think that was good for a baby or toddler."

"They had blankets at that time but I would hear the newborn crying early hours of morning," a Surfers Paradise resident told the Gold Coast Bulletin yesterday. "Why was the baby left with the parents — just why?"

Police found the parents shortly after discovering the body. Photo / Supplied
Police found the parents shortly after discovering the body. Photo / Supplied

Police have now recovered a 2-year-old boy in a "healthy" condition — who is believed to the dead baby's sibling and is now in the care of the state's Department of Child Safety.

Their father, 47, and mother, 23, were found in Broadbeach about 5km away from where the dead baby girl was discovered and were arrested on suspicion of committing an indictable offence.

Child safety advocate Hetty Johnston says there must be a public inquiry into how the baby was left in such a heartbreaking situation.

"The public needs to understand the system they are paying for and how broken it is," the Bravehearts founder told AAP.

"If they (child services) did know about this family, we need to know what happened here. And if they didn't know, then there's something seriously wrong there."

The parents were taken into custody after police attended an alleged domestic violence incident soon after discovering the dead baby.

The couple, who were known to police, had not reported their daughter missing before her body was found.

The homeless parents were known to child safety services. However Child Safety Minister Di Farmer refused to comment on the case, citing privacy.

Opposition Deputy Leader Tim Mander said it would be "incredibly disturbing" if the girl was known to child ­safety services.

"What happened to this little nine-month-old girl was an absolute tragedy," Mr Mander said. "We will await the outcome of police investigations, but if the parents were known to child ­safety and nothing was done then that needs to be made public."

Reverend Jon Brook, of the St John's Church crisis care centre in Surfers Paradise, told the Courier Mail he believed his service had tried to help the couple find affordable accommodation.

"If it's the couple I believe, they were living as rough as it gets — in parks, toilet blocks, under bridges, wherever," he said. "This is just a terrible tragedy. I feel for that poor little child."

The Bulletin revealed that seven months ago, a concerned Surfers Paradise resident told Gold Coast City Council about the homeless family and it was also flagged with welfare services.

Council staff wrote back after five days, apologising for the late reply and telling the resident to raise the matter with other authorities as it was not a council responsibility.

A support worker from homeless services did visit the family but the couple refused help, the Bulletin reported.

The tragedy has cast a heartbreaking light on the scale of the city's homelessness problem.

The 2016 Census showed there were 1723 homeless people on the Gold Coast, a 27 per cent jump since 2011.

The father of the child and her mother have been arrested. Photo / Supplied
The father of the child and her mother have been arrested. Photo / Supplied

Kathleen Vlasic, local co-ordinator of community group Rosies — which has been helping homeless people on the Gold Coast for more than 30 years — said it was the very fact Surfers Paradise was so busy that drew them and others in need of a helping hand.

"It could be 100 to 200 people. It varies from time to time, it's not always the same," Ms Vlasic told the ABC.

"They seem to be able to blend in and not be so noticed all the time. They can wander through Surfers and they're not really going to stand out like a sore toe."

Both parents are in police custody and have been questioned by Queensland homicide detectives but no charges have been laid.

Detective Inspector Marc Hogan said the discovery of the young girl yesterday morning was traumatic for everyone involved.

"This is a very tragic event. It's a very sad situation," he said. "It will impact a lot of people." Insp Hogan said it appeared the girl had been in the water, but there were no obvious wounds or injuries. "Not that I could see," he said describing it as "not your typical crime scene".

"The body was located on the edge of the surf so clearly she had been in the water. I don't know how long for. We will set out trying to find that out today as best we can," he said.

He said drugs weren't a factor in the parents' behaviour but he didn't rule out foul play.

He said the baby did not have any obvious injuries and a ground and air search of the beach yielded little evidence.

Homicide detectives from NSW Police are also involved in the investigation as officers attempt to pin down the couple's movements in that state. Insp Hogan said the child was found less than a kilometre from the main party precinct for schoolies revellers.

A total of 13,188 teenagers made their way to the first night of the annual end-of-year event this weekend and 22,000 graduates are expected to visit the popular holiday spot this week.

Police ruled out any connection to the end of high school celebrations, and it wasn't a school leaver who found the child.

Detectives are checking CCTV footage in the hope the couple and child may have been caught on camera.

- With Wires