The worst fears for Australian 10-year-old Zahra Baker appear to have been realised with police search teams in North Carolina discovering human remains in a bushland grave.

The remains were found on the edge of Gunpowder Creek, a secluded location used by hunters to dump deer carcasses, and a short drive from where Zahra's stepmother, Elisa Baker, once lived.

It is believed police search teams were directed to the site by Mrs Baker, who is being held in custody on an obstruction of justice charge for allegedly writing a fake $US1 million ransom note.

The discovery of the remains came just hours before Zahra's biological mother, Emily Dietrich, flew from Australia to the town of Hickory in North Carolina, the US state where her estranged daughter spent the past two years.

"Search teams in Caldwell County yesterday located evidence that could provide valuable information in the Zahra Baker case," Hickory police said in a statement.

"This evidence will be analysed at the North Carolina State Bureau of Investigation's lab. We understand the concern and interest in this case by the public but we must be cautious in prematurely releasing information so it will not jeopardise any future criminal proceedings."

The discovery of human remains came just over a month since Zahra was reported missing by her biological father, former Queensland sugar mill worker Adam Baker, and followed searches of rubbish tips, ponds, creeks and other bushland areas.

Hickory police would not publicly confirm the find was human remains, but sources did.

Local media reports also said the grave contained body parts, not a complete body.

Police discovered Zahra's prosthetic leg a fortnight ago in another bushland area, while a bone was found during another search.

Zahra had the lower half of her left leg amputated five years ago after being stricken by bone cancer.

Investigators questioned Mr Baker, who was accompanied by his lawyer, for more than an hour on Wednesday at the Hickory Police Department before he was allowed to leave.

Ms Dietrich, in an interview with the Seven Network last week, said she suffered post-natal depression after the birth of Zahra, handed custody to Mr Baker and had no contact with her daughter.

She said she did not know her daughter had moved to the US until three days before Zahra went missing. Ms Dietrich used the internet to track her daughter down.

Mr Baker met Mrs Baker, who is from North Carolina, on the internet. They married in Queensland and two years ago moved with Zahra to North Carolina.

On Thursday, Ms Dietrich, accompanied by a TV crew, inspected a shrine that members of the Hickory community have created in the front yard of Zahra's home.

Neighbours said Ms Dietrich was an emotional mess as she read cards and inspected toys, flowers and other trinkets.

"She was in tears and she said her heart was breaking," neighbour Jennie Bost told local TV station WSOC.

Another neighbour, Eddie Mitchell, told the TV station: "She asked if she could hug me and we hugged and I said to her, 'Just keep going, believe and just keep going."'

A vigil is planned for Zahra in Hickory on Tuesday, which is the date of her 11th birthday.

- AAP