A young girl who suffered a violent death in Brisbane overnight has been described as a high-achieving student who recently won a citizenship award at her grade six graduation ceremony.

Police found the 11-year-old girl dead in an apartment on Dunmore Terrace at Auchenflower in Brisbane’s inner west about 1:40am.

By 5:30am, her mother’s body was found about 1.5 kilometres away at a construction site in Toowong.

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Detective Acting Superintendent Geoff Sheldon said it appeared the girl’s mother had taken her own life.

Both mother and daughter were born in Japan. Police have not yet released their names as they are still trying to notify members of their family in Japan.

The girl was a grade six student at Milton State School.

Milton State School principal Paul Zernike said the girl’s friends would describe her as “a really caring, friendly, lovely, happy student”. Photo: ABC

School principal Paul Zernike said teachers and students were shocked and saddened by the news of her death.

“The student who has deceased was a beautiful young lady,” he said.

“She was a high-achieving student; she was very well liked amongst her peers and right across the school community.

He said her classmates would describe her as “a really caring, friendly, lovely, happy student”.

“They would say that she’s a really good friend to all – in fact she recently won the citizenship award at the graduation ceremony, so a beautiful child,” he said.

He said students at the school were holding up well after hearing of her death and that guidance counsellors and additional teachers and support people were on hand.

Superintendent Sheldon said the girl’s body was found when friends of the family asked police to do a welfare check on their apartment.

“They had some concerns and we’ve gone around, and unfortunately those concerns have been validated to the worst possible degree,” he said.

“Every death of a child is horrendous, but this is particularly so.”

Superintendent Sheldon said the girl’s father, 65, was asleep and uninjured in the unit when police arrived.

The high-rise complex in Auchenflower where the 11-year-old girl’s body was found. Photo: AAP

“He’s been with us all day and assisting us greatly with our inquiries,” he said.

He continued: “His assistance has been of great help trying to work out more about family life, the dynamic, what’s going on around the house, the relationships and the history to this whole tragic scenario.”

The man was released without charge on Tuesday afternoon.

A second daughter, an eight-year-old girl, was not home at the time.

“The mother has appeared at this stage to have taken her own life … in Benson Street, Toowong,” Superintendent Sheldon said.

“We’re seeking public assistance to see if anyone saw her or her vehicle from 11.30 last night until about 1:00am this morning, in and around that area.

“She was driving a 2007 Tiida sedan, a white-coloured sedan.”

He said police could not definitively say who killed the girl.