Honolulu police say that the adoptive parents of 6-year-old Isabella Kalua, also known as Ariel Sellers, killed her sometime around mid-August and reported her missing a month later.

Both parents were arrested Wednesday for suspicion of second-­degree murder and charged as part of an FBI and Honolulu police investigation into the child’s disappearance. Both are being held without bail. Authorities have not recovered her body, but continue to search the Kalua’s Waimanalo property.

Police arrested Lehua Kalua, 43, at 7:30 a.m. at 41-610 Puha St. during an FBI and police raid of her Waima­nalo home.

Her husband, Isaac K. Kalua III, 52, was arrested at 7:10 a.m. on suspicion of second-degree murder in Building 167 at Pearl Harbor Naval Shipyard, where he works.

Police said that from their analysis, they have determined Isabella, who they referred to as Ariel on Wednesday, likely died in mid- August — a full month before the Kaluas made a 911 call at 6:25 a.m. on Sept. 13 to report her missing.

Police want anyone who saw the couple between August and September to call with information that may lead them to Isabella’s remains.

Armed with a search warrant, police and the FBI swarmed the Kaluas’ Waimanalo home and seized items from the house and the couple’s vehicles. Authorities will likely continue searching the property through today.

Maj. Ben Moszkowicz, commander of HPD’s Criminal Investigation Division, and homicide Lt. Deena Thoemmes said police have followed up on every lead received and will continue to follow up on new information. Nothing is being ruled out, including possible accomplices who might have helped hide the body. However, at this time they believe the Kaluas are the only suspects.

Moszkowicz credited the FBI’s Behavioral Analysis Unit that gave police insight into the case.

“We gave them a bunch of evidence, but they turned around and gave it back to us and said, ‘Maybe look at it from this angle or when you talk to this person, talk about this,’ ” he said. “Very slight change to the tack that the homicide team was taking was able to create this development.”

Since the case is not being charged federally, but by the state, HPD had to take into account any evidence gathered by the FBI that could be disqualified because it was gained without a warrant.

Thoemmes said police had suspected foul play some weeks ago.

“In a case like this we’re going to look at everything and question everything,” she said. “So there were some things that just didn’t add up for us and we just followed up with what we believed and followed up with what the evidence suggested to us.”

Initially the Kaluas allowed police to search their house and were cooperative, but later they failed to call police back. At some point HPD needed a search warrant “to do what we needed to do,” requiring approval by the Honolulu Prosecutor’s Office and a judge, Thoemmes said.

“But at that time we had a missing person case, so we had to build our probable cause to get a criminal case to get a search warrant for a search of the premises,” she said.

However, Thoemmes did not reveal what specific evidence led police to Wednesday’s search.

Police also did not discuss their interviews with Isabella’s biological sisters, who also lived in the Kalua household. The three sisters, ages 12, 3 and 1, were either adopted or fostered by the Kaluas.

Police had the three children removed from the home after Isabella was reported missing, and they are in the custody of state Child Welfare Services.

Moszkowicz said the time of Isabella’s death was determined by the pattern of activity police were able to detect by talking to cooperating witnesses and other evidence. “We can’t find any cooperating witnesses who could tell us they had seen her after that,” he said.

Police would like any witnesses to come forward who interacted with the family to see whether there were any signs of abuse from 2019 to August.

Attorney William Harrison, who has previously spoken on behalf of the Kaluas, could not be reached Wednesday for comment.

Biological mother Melanie Joseph, who spoke of seeing Ariel with bruises, smashed fingers and other signs of abuse shortly after the disappearance was reported, declined to talk with the Honolulu Star-Advertiser on Wednesday afternoon, saying, “Now is not a good time.”

Her cousin Taryn Napoleon said Joseph is taking the news hard.

“It’s something we wanted,” she said. “We want closure. We want to bring her home, but it’s bittersweet.”

She said all the biological relatives held out hope the child was still alive.

“We just want her home,” she said. “We’re waiting for her to come home. It’s very hard to hear, very hard to accept. She’s a baby. She had her whole life ahead of her. It’s not fair.”

Thoemmes said a break in the case occurred late last week and it was then that the case was technically reclassified to a murder from a missing persons case. However, she said she could not provide further details.

The statement the Kaluas initially made to police was false, that the girl had left the house in the middle of the night, and that was proven false from a review of multiple surveillance videos in the area, Thoemmes said.

She said the Kaluas told police that on Sept. 13 that Isabella left the house in the middle of the night, “walked away.”

Moszkowicz said certain details cannot be shared with the public. “Because of the need for secrecy, it can very well look from outside like Ariel had been forgotten or not enough resources were being devoted to finding out what had happened to this poor little girl,” but he said, “nothing could be further from the truth.”

“Prematurely had we revealed in the last day or two that instead of investigating a missing person that we were investigating a murder, that may have prevented … the progress we were able to make that led us to crack the case,” he said. “It frustrates us as well that we face scrutiny and headlines that make it look like we’re not doing anything.”

“Hundreds of thousands of hours have gone into the case,” he said.