An American woman accused of killing seven babies she gave birth to over a decade has been arrested after police discovered the tiny bodies stuffed in cardboard boxes in the garage of her former home.

Megan Huntsman, 39, who lived in the house in Utah until three years ago, had the infants between 1996 and 2006, investigators said on Sunday.

Officers responded to a call on Saturday from Huntsman's estranged husband about a dead infant at the home in Pleasant Grove, a middle-class area just south of Salt Lake City, police Captain Michael Roberts said. Officers then discovered the six other bodies.

Roberts declined to comment on a motive and what Huntsman said during an interview with investigators.

Neighbours said they were shocked by the accusations and perplexed that the woman's older children still living in the home didn't know their mother was pregnant or notice anything suspicious.

The police spokesman said the estranged husband lived with Huntsman when the babies were born but isn't a person of interest at this time. The man's name was not immediately released.

"We don't believe he had any knowledge of the situation," Roberts told The Associated Press.

Asked how the man could not have known if he lived in the house, Roberts replied, "That's the million-dollar question. Amazing."

The babies' bodies were sent to the Utah medical examiner's office for tests, including one to determine the cause of death. DNA samples taken from the suspect and her husband will determine definitively whether the two are the parents, as investigators believe.

The house is owned by the husband's parents, and the man was cleaning out the garage when he made the grisly discovery.

Huntsman's three daughters still live there, longtime neighbour Sharon Chipman told The Salt Lake Tribune. The oldest are around 18- to 20-years-old, while the youngest is about 13, she said.

Huntsman was a great neighbour, and Chipman trusted her to watch her grandson when he was a toddler, Chipman added.

"She took good care of him. She was good. This really shocks me," Chipman told The Tribune.

Roberts said the case has been "emotionally draining" and upsetting to investigators. He was at the home when the bodies were discovered.

"My personal reaction? Just shocked. Couldn't believe it. The other officers felt the same," he said.

Huntsman was booked Sunday into the Utah County Jail on six counts of murder. Roberts said it wasn't clear if she has an attorney.