The parents of an 11-year-old girl who suffered a 'violent and horrific death' hours before her Japanese mother killed herself were having 'relationship issues', according to police.

Detectives found Celeste Pearson's body in the bathroom of her family's Brisbane penthouse at around 2.30am on Tuesday after concerned friends raised the alarm, according to The Courier Mail.

Her mother, Chiaki Pearson, 49, fled the scene in Auchenflower, prompting a major search which ended when her body was found at the base of a crane in Toowong just before 5.30am on Tuesday.

The 11-year-old's property developer father Chris, 65, has spent the day helping police with the investigation and it has emerged there was a history of domestic violence between the parents.

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Detectives found Celeste Pearson's body in the bathroom of her family's Brisbane penthouse (pictured) at around 2.30am on Tuesday after concerned friends raised the alarm

'There was a call from concerned people just to go and check on how they were,' Detective Superintendent Geoff Sheldon said.

'There were some issues in relation to the relationship earlier that night. So police have gone around and been confronted with the deceased child.'

Sheryl Hall, who cleans several units at the high-rise, described the two young girls who lived inside the apartment as 'quiet and polite', but said their parents were having difficulties..

'They are beautifully well-behaved children,' she said, according to The Age.

Police have asked for anyone who knew the family to come forward to help shed more light on their domestic life.

'If you know any of the family yourself ... we'd be keen to hear what you can tell us that might fit together with the piece of information that we're looking for,' Supt Sheldon said.

The 11-year-old girl's father, who was asleep in his bedroom when police arrived, has been helping police better understand the 'family dynamic'.

He claimed the first he knew of his daughter's violent death was when officers knocked on his apartment door for a welfare check, according to police.

The girl's 49-year-old mother could not be located when police arrived but she was found dead a few hours later in the nearby suburb of Toowong (pictured)

Police guard the entrance to a high-rise apartment block where an 11-year-old girl was found dead in the bathroom at 1.45am on Tuesday

Friends of the family have arrived at their home to lay flowers and tributes.

One woman told the Courier Mail that the mother, who was born in Japan, was 'the loveliest person'.

'She really just does everything for everyone,' the woman said.

The mother's body was found by members of the public outside at the bottom of a crane just a few blocks away from the Coronation Towers high-rise.

She is believed to have jumped to her death.

Her 11-year-old daughter has been remembered as a 'high achieving and friendly' young girl by students and staff at her school.

Paul Zernike, the Principal of Milton State School, said support has been offered to her friends, fellow students and staff at the school.

'She was an enthusiastic, high achieving and friendly young child who will be greatly missed by all her friends and teacher,' he said in a statement.

'Our thoughts and sympathies go out to the family, caregivers, friends and loved ones during this difficult time.'

Supt Sheldon described the young girl's death as 'horrific' and 'violent'.

'We have a family that has literally been decimated. It's an appalling tragedy that two members of this family are now deceased,' he said.

The girl has an eight-year-old sister who was not at the apartment block at the time.

Superintendent Geoff Sheldon described the young girl's death as 'horrific' and 'violent'

The body of an 11-year-old girl was found at this Brisbane apartment complex and her mother was found hours later in a nearby suburb after taking her own life

Det Supt Sheldon said it was still unclear whether the incident was a murder or murder-suicide, saying police are keeping an 'open mind'.

Neighbours said they were 'concerned' about what was happening inside the apartment block when they called emergency service, Det Supt Sheldon said.

Police have also appealed for anyone who saw a white sedan driving around the Toowong and Auchenflower area between 11.45pm and 1am to contact crime stoppers.

Detectives said the family was not known to them saying the deaths had 'come from left field'.

The family reportedly lived in the penthouse of the apartment block and were originally from Japan, according to Nine News.

For support and information about suicide prevention call Lifeline on 13 11 14.

Police guard the car belonging to a 49-year-old woman found dead near Brisbane this morning

Detectives interviewed workers outside the Auchenflower apartment block on Tuesday after the girl was found inside and her mother was found dead in the nearby suburb of Toowong