Parents charged with murder of their adopted daughter kept her in a cage, duct-taped her mouth, and tried to keep her death a secret, sister told police

• Isabella Kalua's sister told police she saw her sister in a dog cage in her home, documents show.
• Isabella had duct tape on her nose and mouth and was not breathing, the girl said.
• Isabella's adoptive parents reported her missing, but were later charged with her murder.

The adoptive parents of a six-year-old girl kept her in a dog cage in their home in Hawaii, and appeared to try to cover up her death, the girl's sister told police.

The description of Isabella Kalua was contained in a criminal complaint against Lehua and Isaac Kalua, the adoptive parents who reported her missing and were later charged with murdering her.

The complaint included details of an interview the Honolulu Police Department carried out with Isabella's elder sister, who was not named and is around 11 years old. It was published by the Honolulu Star-Advertiser newspaper.

The sister described seeing Isabella lifeless in a dog cage with duct tape on her nose and mouth about two months ago, before she was reported missing.

The sister said Lehua, adoptive mother to both girls, asked her to keep what she saw a secret.

According to the court documents, the sister alleged that Lehua Kalua filled a bathtub with water to try and wake Isabella. She did not wake up, per the complaint.

Isabella was reported missing on September 13 by Lehua and Isaac Kalua. Per the complaint, they told police they last saw her when putting her to bed on September 12.

This and other information the Kaluas gave was later found to be false, Honolulu police officer Deena Thoemmes told a press conference on Wednesday announcing their arrest.

The Kaluas appeared in court on Friday and pleaded not guilty, according to Hawaii News Now. Police said they are the sole suspects in her death.

Isabella was last seen on surveillance footage on August 18. According to Honolulu police, she may have been killed as long as a month before the missing-person report. The sister in her interview could not give precise dates for what she saw.

She said that the Kaluas routinely used a dog cage to contain Isabella, hoping to prevent her from sneaking around at night to find food because she was hungry, the complaint said. She said Isabella was hungry because Lehua didn't feed her.

The sister told police that she was there when the dog cage was ordered online, and noted that he family did not have a pet, per the complaint.

The sister said that she believed the duct tape came from her adoptive father's job at Pearl Harbor shipyard. She alleged that Isabella had been duct-taped "plenty of times" before.