SKOWHEGAN, Maine — The 20-year-old Fairfield mother charged with murder in the death of her newborn son on Dec. 31 either smothered him or allowed him to die of exposure, a prosecutor told a Superior Court judge Friday.

Justice Robert Murray found probable cause for a murder charge against Kayla Stewart and ordered that she continue to be held at the Somerset County Jail without bail.

The remains of a full-term infant with the umbilical cord attached were found in the unheated, detached, single-car garage near the home Stewart shared with her boyfriend Nicholas Blood, 25, of Fairfield, Maine State Police detective Scott Bryant said in affidavit filed Friday.

On Jan. 11, police found the remains wrapped in a blanket and trash bags, hidden under an oil tank in the garage, the affidavit said. Blood-stained bedding, paper towels and plastic gloves were found in the garage near the oil tank.

A DNA test determined that Blood most likely was the father of the baby boy. Blood has not been charged in connection with his son’s death. He and Stewart have a 3-year-old son who now is living with other relatives, according to previously published reports.

Stewart is charged with intentional or knowing murder or, in the alternative, depraved indifference murder but has not entered pleas because she has not yet been indicted by the Somerset County grand jury.

Stewart was arrested on Jan. 22 at her home on Route 139 in Fairfield.

Defense attorney Pamela Ames of Waterville told Murray that Stewart thought the child was stillborn because the baby’s eyes were closed and he was not moving.

Ames asked that Stewart be released on $10,000 surety or $1,000 cash bail with strict conditions that might include house arrest and electronic monitoring.

Assistant Attorney General John Alsop, who is prosecuting the case, told the judge that the medical examiner found the child was born full-term and alive. The baby died of asphyxiation, Alsop told the judge.

The prosecutor argued that Stewart should be held without bail.

“She took no steps to seek medical attention,” the prosecutor said. “She clearly had a duty of care to the newborn. She either suffocated or smothered or somehow deprived him of oxygen or she put a still-living baby in a garbage bag in an unheated garage, knowing he would surely die there.”

The investigation that led to Stewart’s arrest began Jan. 10 when Kayla Stewart’s mother, Lucille Stewart, 57, of Fairfield, called police to ask that they investigate whether something might have happened to the baby her daughter had been carrying, the affidavit said. The elder Stewart woman told police her daughter learned in late November or early December that she was pregnant after being X-rayed following a fall at work. Kayla Stewart allegedly told her mother that she was 3½ months along and the baby had no heartbeat, so she was waiting to miscarry or have a medical procedure.

Lucille Stewart told investigators she became concerned because her daughter still was on her insurance and she’d received no information about any procedures or doctor visits, the affidavit said.

In interviews with police, Kayla Stewart told several stories, including that she had miscarried in the toilet and flushed the fetus away, according to the affidavit. Eventually, she told police that she had given birth in the garage and believed the baby was dead because his eyes were closed, he was not moving and he was not breathing. Stewart also told police where the remains were hidden.

Dressed in jail clothes with her feet shackled and her wrists handcuffed, Stewart sobbed when the judge ordered she be held without bail.

Murray said the issue of bail could be revisited.

Family members attended the hearing but declined to speak with reporters.

If convicted of murder, Stewart faces between 25 years and life in prison.