(CNN) -- Police in Mobile, Alabama, said Sunday they are "actively searching" for the bodies of two young children believed killed by their father and stepmother.
Authorities began investigating a missing persons report on Jonathan DeBlase, 3, and his older sister Natalie, 4, on November 19. However, the children have not been seen since late June, said Officer Christopher Levy, spokesman for Mobile police.
The children's father, John Joseph DeBlase, 27, was arrested Friday. He faces two counts of aggravated child abuse and two counts of abuse of a corpse, Mobile police said in a statement. Stepmother Heather Keaton was arrested earlier in Louisville, Kentucky, and faces two counts of willful abuse and neglect of a child, police said.
Keaton went to police in Kentucky and asked for a restraining order against DeBlase. The couple had been living in Louisville, Kentucky, but had apparently separated, Levy said.
According to police documents from Louisville, Keaton told investigators she felt DeBlase "may have murdered his children because he said that they were nonresponsive," CNN affiliate WKRG reported. She said DeBlase had told her "choices were made ... and he had to do what he had to do."
Keaton told police she feared for her own life because of events that took place six months prior in Mobile, Levy said. "When she was explaining why she needed this emergency order of protection from him ... it was told to them (investigators) that the kids were dead and it had occurred in Mobile."
WKRG said Keaton approached authorities November 18. Levy said police were notified and began investigating a day later.
Keaton, identified as Heather Leavell-Keaton by WKRG, was arrested Tuesday night, and police began looking for DeBlase.
On Friday, Mobile police were notified by the Santa Rosa County, Florida, Sheriff's Department that DeBlase had been found, police said. He was returned to Mobile.
"Detectives have determined that both John DeBlase and Heather Keaton are responsible" for the children's deaths, the Mobile police statement said. "Police will continue to search for the children."
Mobile Police Chief Micheal T. Williams told reporters Friday that police believe the children are dead, based on what DeBlase has told them.
"He's given us an indication of a location where they may be, where he remembers burying the children," Williams said. A team of investigators, searchers and cadaver dogs would be looking in the area over the next few days, he said.
Williams would tell reporters only that the location was within 100 miles of Mobile. But the Mobile Press-Register newspaper reported that searchers on Saturday looked for the bodies near Vancleave, Mississippi.
Asked about the corpse-abuse charge, Williams told reporters, "It certainly means that there has to be a dead body, so that body was treated in a manner that wasn't consistent with the way that we normally treat our deceased."
Levy said Sunday the corpse-abuse charge was "going to be more in reference to him taking their bodies and leaving them in the woods."
Jackson County, Mississippi, Sheriff Mike Byrd told the Press-Register on Saturday that the boy's body might have been tossed on the side of a Mississippi road.
"From what we understand, the father was going to bury the child about six months ago. He had a shovel and everything, but the ground was too hard," Byrd told the newspaper. "He's not real sure where. Whether he's telling us the truth or not, we just don't know."
Byrd said Keaton and DeBlase have each accused the other of killing the children. The two agree that at least one child's body is in the Vancleave area, he said, according to the Press-Register.
Attempts by CNN to contact Byrd on Sunday were not immediately successful.
Williams said Friday that DeBlase was being "somewhat cooperative," and police want to gain as much information as they can while his cooperation lasts.
"We are actively searching," Levy said Sunday. Police still aren't sure about the circumstances leading up to the deaths of the children, he said.
Keaton waived extradition in a court hearing Wednesday in Kentucky, WKRG reported. She will be brought to Mobile to face the charges against her.
The children's mother, Corrine Heathcock of Mobile, told WKRG on Thursday that she hadn't seen her children in more than a year. DeBlase took the two children when the couple divorced, she said. "I didn't have a steady place to live. I didn't have a job." She said when she attempted to see the children, DeBlase picked fights with her and stopped answering the phone.
Heathcock pleaded publicly for her ex-husband to come forward as police were searching for him. "Turn yourself in," she said. "Where's my children at? I want them home ... if they're dead, I want to bury them. They deserve that."
Asked how no concerns were raised despite the children not being seen in months, Levy said, "No family members, no friends, no neighbors, none of them reported them missing ... And that's probably one of the most disturbing parts of the whole thing, that we're finding out six months later that they've been gone."
He said several people have come forward in the media and said they believed the children were being abused, but did not notify anyone.
"That's my question for them, is 'Where were you a year ago when they were actually in danger?'" he said.
CNN Radio's April Williams and CNN's Rick Martin contributed to this report.