Fears grow for missing Hawaii girl, 6, whose adoptive parents say they last saw her when they put her to bed on Sunday as it's revealed that they had pulled her out of school 

• Isabella 'Ariel' Kalua, 6, of Oahu in Hawaii was last seen on Sunday night by her adoptive parents when they put her to bed 
• The Department of Education for Waimanalo reported the girl had been withdrawn from school to be homeschooled
• Her biological mother reported another mother told her Kalua had been missing from school for a week 
• Her adoptive parents Sonny and Lehua reported the girl missing on Monday  
• An AMBER alert has not been issued because there is 'insufficient evidence' that she has been abducted, police said
• Hundreds of volunteers are combing the Waimanalo region of the island in hopes of finding the girl - on Wednesday, the FBI joined search efforts 
• 'We're hoping she's not in immediate danger,' Waimanalo Interim Police Chief Rade Vanic told news outlets 
• 'I just want whoever has her to bring my baby back home,' Isabella's biological mom, Melanie Joseph, told volunteers on Wednesday 

Hundreds of volunteers are combing a region on the Hawaiian island of Oahu in search of a missing six-year-old girl, as it was revealed her adoptive parents pulled her out of school for a week. 

Isabella 'Ariel' Kalua's adoptive parents Sonny and Lehua filed paperwork citing homeschooling as the reason for their daughter's withdrawal, a Department of Education representative told Honolulu Star-Advertiser. 

Further information on when Kalua was withdrawn have not been shared.  

Kalua's biological mother Melanie Joseph was reportedly told by another mother that she hadn't been to school in a week. 

A private investigator Steve Lane said the lack of oversight over homeschooled children is problematic. 

'There's not requirement to check if the parents are qualified. That's why kids die,' he told the Honolulu Star-Advertiser. 

He cited a different case of another homeschooled Hawaiian girl who was starved to death by her parents and grandmother. 

Homeschooled children have lower chances of someone recognizing evidence of abuse or neglect, according to Lane.  

This is even more important in Kalua's case whose adopted father has a felony and has been convicted of two second-degree assaults, an attempted second-degree assault, and a first-degree terroristic threatening, according to the Honolulu Star-Advertiser. 

Sonny has been approved to foster four of Joseph's daughters after she lost her children due to drug abuse. 

'How did those kids ever get that house?' Lane said to the Honolulu Star-Advertiser. 'You can't put kids in that kind of household.' 

Video footage of a small child walked alone outside at 12.45pm, followed by two adults may show Kalua's abduction. 

Footage showed cars continuously going around the neighborhood in Kailua. 

As of Wednesday, Honolulu Interim Police Chief Rade Vanic said that the department '[doesn't] have sufficient evidence' to show that Isabella 'Ariel' Kalua has been abducted, according to Hawaii News Now.

'We're hoping she's not in immediate danger,' he told the outlet.

Isabella's adoptive family reported her missing on Monday morning, Vanic said - an AMBER alert has not yet been issued because the criterion for abduction 'was not met.'

The adoptive family told KHON 2 on Monday that they were 'told not to talk to investigators,' and did not proffer further details.

Despite hundreds of volunteers searching the community, tying purple ribbons around trees to indicate that those areas have already been covered, the child still has not been found after three days.

'I’m thankful everyone is here to help,' Melanie Joseph, Isabella’s biological mom, told volunteers converging at Waimanalo's District Park after a fruitless day of searching on Wednesday. 'I just want whoever has her to bring my baby back home.'

The FBI announced Wednesday that they would join in search efforts. 

'She’s not a wanderer, so this is very surprising me to us, out of character,' Isabella's biological aunt, Jamie Kumai, told KHON 2. 

'The truth will come out, and it will come out soon because the heat is hot in Waimanalo, and it’s hot and we’re coming.'

Kumai said she flew in from Maui to join the search when she heard her niece had gone missing, according to KHON 2. 

'We're still trying to keep positive and have faith during this time - we're not giving up hope and we don't want to think of the worst,' Kumai said.

Other volunteers and family members are less optimistic, but still vigilant in their search.

'I’m very candid. I don’t sugarcoat nothing,' said Alena Kaeo, one of Isabella's biological aunts, to Hawaii News Now on Wednesday. 

'Regardless of what the outcome is, we just want to bring her home for some kind of closure.'

Area police are asking residents to check places small enough for a small child to hide, and their security footage if they have it.

The girl stands at 3-foot-3, weighs 46 pounds and was wearing a black hoodie, leggings, colorful socks and Nike slides with pink bottoms when she was last seen. 

Volunteers Blake and Ashley Caporoz of Makaha joined the search party Wednesday, although they don't know Isabella or her family.

'We have a 6-year-old and we would want community help from the other side as well,' Blake Caporoz said to Hawaii News Now.

'I don’t know the family but as a mother I know how Hawaii is,” said another parent, Shonna Hammoan, to KHON 2.

'The community always surrounds each other. So I have a 17-year-old and a 21-year-old daughter. I know people would come out and help. So I was compelled to come out and search for her today.'