An initial post-mortem of Bobbi Kristina Brown has found no significant injuries and no obvious underlying cause of death, says a medical examiner.

Ms Brown, the daughter of late singer Whitney Houston, died on Sunday after spending months in a medically induced coma.

The 22-year-old was found unresponsive in a bathtub in her Atlanta home on 31 January.

The incident was described as a "drowning" by police, and doctors said Ms Brown had suffered irreversible brain damage.

A $10m civil lawsuit filed last month accused Ms Brown's partner Nick Gordon of causing her life-threatening injuries and stealing from her bank account while she was in a coma.

No charges have been filed in the case.

In a statement on Monday morning, the Fulton County Medical Examiner's Office said the time that elapsed from when Ms Brown was found unresponsive until her death would "complicate" its effort to reconstruct events.

Ms Brown was found face down in the bathtub at the home she shared with Mr Gordon, who was her adopted brother.

The couple had regularly referred to themselves as husband and wife in public, but family members claim they were never married.

'Krissy'

Bobbi Kristina - referred to as Krissy by family members - was the only child of Houston and Bobby Brown, and was treated in hospital twice for anxiety after her mother passed away.

She spent months in a medically induced coma and was moved into hospice care in Georgia in June, but never regained consciousness.

Her death was confirmed in a statement on Whitney Houston's official Facebook page, which read: "It is hard to say goodbye."

"On Sunday, July 26, Bobbi Kristina Brown made her transition peacefully. The family thanks everyone for their loving thoughts and prayers."

"As Bobbi Kristina would say: 'The wind is behind me and the sun is in my face'."

This photo was also posted on the late singer's page:

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In an interview with Oprah Winfrey shortly after her mother's death, Ms Brown had spoken of her aspirations to carry on her mother's legacy by forging a career in dancing, acting and singing. However, her career never took off.

Jeanne Wolf, a Hollywood reporter who had met Bobbi Kristina and her late mother, said that the young woman's death was "a long time coming".

The journalist explained: "She never had anything that approached a normal life. She was surrounded by a husband and wife that were fighting, she was surrounded by drugs and people trying to get off drugs."

"None of this is wholesome living, none of this is something you can say with a smile."

After news of the young woman's death emerged, Winfrey tweeted: "Peace at last!"

Peace at Last! #BobbiKristina

— Oprah Winfrey (@Oprah) July 27, 2015

The Grammy-winning performer Missy Elliot tweeted: "My heart is truly heavy. May u rest in peace with your mommy #BobbiKristina sending prayers 2 the Brown/Houston family."

My heart is truly heavy ?? May u rest in peace with your mommy #BobbiKristina sending prayers 2 the Brown/Houston family????

— Missy Elliott (@MissyElliott) July 27, 2015

Rest in peace #BobbiKristina ???? pic.twitter.com/QLMk2paF9S

— Puff Daddy (@iamdiddy) July 27, 2015

Rest in peace #BobbiKristina ????

— NE-YO!! (@NeYoCompound) July 27, 2015