The investigation into the death of a baby who authorities believe was heated in a microwave oven was difficult because of a lack of research on the effect of microwaves on people, a coroner's official said.

China Arnold, 26, was jailed Monday on a charge of aggravated murder, more than a year after she brought her dead month-old baby daughter to a hospital on Aug. 30, 2005, police said.

"We have reason to believe, and we have some forensic evidence that is consistent with our belief, that a microwave oven was used in this death," said Ken Betz, director of the Montgomery County coroner's office.

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He said the evidence included high-heat internal injuries and the absence of external burn marks on the baby, Paris Talley.

That conclusion is supported by the Dayton police investigation, he said.

The death was ruled a homicide caused by hyperthermia, or high body temperature. The lack of external burns ruled out an open flame, scalding water, heating pad or other possible cause of death that would have damaged the skin, Betz said.

Arnold's lawyer, Jon Paul Rion, said she had nothing to do with her daughter's death. She was stunned when investigators told her that a microwave might have been involved, he said.

"China — as a mother and a person — was horrified that such an act could occur," Rion said.

Arnold was arrested initially after the baby's death, then released.

There was a lengthy investigation before prosecutors found enough probable cause to issue another arrest warrant, said Greg Flannagan, a spokesman for the county prosecutor's office.

A microwave was taken as evidence, police Sgt. Gary White said.

Municipal Judge Bill Littlejohn set Arnold's bond Tuesday at $1 million. Arnold participated in the hearing from the county jail by a video hookup, giving "yes" and "no" answers to procedural questions. She declined interviews through her attorney, who said his client plans to plead not guilty.

In 2000, a Virginia woman was sentenced to five years in prison for killing her month-old son in a microwave oven. Elizabeth Renee Otte claimed she had no memory of cramming her son in the microwave and turning on the appliance in 1999. Experts said that Otte suffered from epilepsy and that her seizures were followed by blackouts.

Nerve damage can occur quickly with microwave injuries, said Louis Bloomfield, a professor of physics at the University of Virginia.

The ovens' electromagnetic waves cook primarily through the presence of water in food, the water molecules heating up as they are twisted back and forth about 2.5 billion times a second, he said.

The night before Paris Talley was taken to the hospital, Arnold and the child's father went out for a short time and left Paris with a baby sitter, Rion said.

The mother did not sense anything out of the ordinary until the next morning, when the child was found unconscious, Rion said.

The baby's father, Terrell Talley, said his daughter was fine when he and Arnold arrived home after leaving her in the care of the baby sitter, his sister.

"When I went in the house, my baby was sitting in the car seat, she was asleep and she was alive," he said. "The babysitter ain't had nothing to do with it."

His sister, Lionda Talley, did not return a call for comment.

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