PLEASANT GROVE, Utah— Megan Huntsman was clear about what she did with six of her newborn babies.

Huntsman, 39, told police she either strangled or suffocated them immediately after they were born. She wrapped their bodies in a towel or a shirt, put them in plastic bags and then packed them inside boxes in the garage of her home south of Salt Lake City.

Megan Huntsman is shown in this booking photo provided by the Pleasant Grove County Jail in Pleasant Grove, Utah April 13, 2014. Huntsman was arrested and booked on suspicion of murder early April 13, 2014 after police found the decomposing bodies of seven infants stuffed in separate cardboard boxes in her former home.[Photo/Agencies]

What's not clear is why. A day after her arrest on charges of killing her six babies, investigators and her neighbors puzzled over the grisly discovery, including how she could have concealed a half-dozen pregnancies over a 10-year period.

"How can you have a baby and not have evidence and other people know?" asked neighbor SanDee Wall. "You can't plan when a baby is going to come. Just the thought of somebody putting a baby into a box is a heartbreaker."

Huntsman, who was arrested Sunday on six counts of murder, was ordered held on $6 million bail — $1 million for each baby. The remains of a seventh baby police found appears to have been stillborn, authorities said.

According to a probable cause statement released by police Monday, Huntsman said she gave birth to at least seven babies between 1996 and 2006 at her former home in Pleasant Grove, a leafy, sleepy town about 35 miles south of Salt Lake City.

All but one of the babies was born alive, she said. During the interview with police, she was unemotional and matter of fact, according to Pleasant Grove police Lt. Britt Smith.

Her estranged husband, Darren West, made the discovery Saturday with fellow family members while cleaning out the garage of the house, which is owned by his parents. He called Huntsman, who admitted to him it was her baby, according to court documents.

West called police, who then found the bodies in the garage.

Investigators believe Huntsman is the mother of them all based on what she has told them but have ordered DNA tests to make sure that's the case. They don't know who the babies' fathers are. It could take weeks to get the results, Utah County Attorney Jeff Buhman said.

Huntsman's three daughters — one teenager and two young adults — also lived in the house.

Investigators believe West and Huntsman were together when the babies were born, but don't believe he was aware of the killings. Buhman said Huntsman is the principle suspect, but didn't rule out more arrests as the investigation continues.

Police have talked with West as they investigate his level of knowledge and involvement in the deaths, Smith said. He was living in the house during the decade that authorities believe Huntsman had killed the babies, Smith said.

He's been cooperative, and was devastated by the discovery, he said.