This file photo provided by the Utah County jail shows Megan Huntsman, who was booked into the Utah County jail on suspicion of killing six of her newborn
This file photo provided by the Utah County jail shows Megan Huntsman, who was booked into the Utah County jail on suspicion of killing six of her newborn children over the past decade. Seven dead babies were found in a garage at a Pleasant Grove home where Huntsman lived up until 2011. (AP Photo/Utah County Jail)

PROVO, Utah - Prosecutors have filed six first-degree murder charges against a Utah woman accused of killing six babies after giving birth to them, and keeping their bodies in boxes in her garage.

The charges were filed Monday morning shortly before 39-year-old Megan Huntsman appeared in court for the second time. She was informed of the charges during the brief hearing.

Prosecutors say Huntsman is the only suspect in the deaths of the babies. They say a seventh dead infant found in the garage appears to have been stillborn.

Investigators believe Huntsman's estranged husband, Darren West, is the babies' father, though they are awaiting DNA results to confirm that. West is not a suspect.

Huntsman is being held on $6 million bail.

Authorities say they think they know her motive, but they have declined to reveal it publicly.