DETROIT » A brother and sister whose bodies were found in a deep freezer in their Detroit home had been beaten to death, autopsies determined Friday, painting a more complete picture of the horrors that unfolded inside the home for years but that apparently went unnoticed by the outside world.

The Wayne County medical examiner’s office classified the deaths of Stoni Ann Blair and Stephen Gage Berry as homicides, saying both were killed by multiple blows and that the young boy also had "thermal injuries."

Their older sister, who is 17, told child welfare officials that their mother, Mitchelle Blair, tortured Stephen "for approximately two weeks prior to his death by tying a belt around his neck, throwing hot water on him while in the shower and putting a plastic bag over his head." The girl and Blair’s other surviving child, an 8-year-old boy, have been placed in the care of a relative.

Blair, 35, is jailed on first-degree child abuse charges, but prosecutors said Thursday that she could face murder charges depending on what the autopsies found. The prosecutor’s office said Friday that there would be no changes in the charges over the weekend.

Investigators believe Stoni was 13 when she died and Stephen was 9. They think Stephen died in August 2012 and that Stoni died the following May.

In a court filing Thursday to end Blair’s parental rights, the state Department of Human Services quoted her surviving daughter as saying that after Blair killed Stephen, his body was wrapped in a bed linen and put in the freezer.

She said in May 2013, Stoni incensed their mother by saying she didn’t like either of the surviving siblings, and that their mother strangled Stoni with a T-shirt and placed a plastic bag over her mouth. The older girl said her mother forced her to put her sister’s body in the freezer, the agency wrote.

Court officers carrying out an eviction notice at the family’s home in an apartment complex near downtown Detroit on Tuesday found the bodies in the freezer. Neighbors said afterward that they hadn’t seen the dead children for about a year — although investigators believe it must have been longer than that — and that they rarely saw the two surviving children. When neighbors asked if the children attended school, they said Blair told them the kids were being homeschooled.

The 17-year-old told child welfare officials that she attended elementary school and middle school, but that neither she nor her siblings had gone to school in two years. It’s not clear if they actually were receiving lessons at home.

Under Michigan’s school code, parents and guardians can take their children from public schools and homeschool them without alerting local or state education officials.

City Councilwoman Mary Sheffield said Friday that’s not good enough.

"There is no accountability whatsoever," Sheffield told The Associated Press. "You can pull your student out (of school), but there is no way to monitor the care and well-being of that child. That’s a huge concern."

Sheffield, who held a prayer vigil Friday night at the family’s apartment complex, said she will be working with state legislators to take a closer look at the law.

The issue gained some attention briefly in 2013, when a bill was introduced in the state House that would have required parents to register their homeschool with the state.

"But it didn’t go anywhere," said Bill DiSessa, state Education spokesman.

Gilda Jacobs, chief executive of the Michigan League for Public Policy, said it’s too easy under the current system for children to fall through the cracks.

"Nobody knows what goes on inside certain homes, and there is literally no accountability built into the homeschooling process," said Jacobs, whose Lansing-based organization is an advocacy group for the poor.

Angela Gordon, an aunt who is caring for the two surviving children, said her first priority is enrolling them in school. She said she had no indication anything was wrong at the apartment but questioned whether home checks were completed by the state.

The state said in its court filing that Child Protective Services had contacts with the family in 2002 and 2005, and that investigations substantiated allegations of physical abuse. Neither of the fathers were involved in the four children’s lives, and both owe more than $10,000 in child support, the agency noted.

Blair also collected government food assistance and Medicaid for all of her children — including Stoni and Stephen — through this month.

"While we cannot release information on a specific case, this type of tragedy underscores that protecting children is the responsibility of everyone in our communities," said Bob Wheaton, state Human Services spokesman. "We rely on the eyes and ears of those in the community to help us protect children."

Michigan Department of Human Services abuse and neglect hotline: 1-855-444-3911.