A 14-year-old girl was arrested late Thursday on a first-degree murder charge after her mother found the teen's dead newborn baby in a shoebox among her laundry items, according to Polk County deputies.

The girl told detectives Cassidy Goodson began to feel sick on Sept. 17. Deputies said two days later, the teen went into labor in her bathroom. Goodson said she placed a towel in her mouth and turned on the bathroom water to conceal any noise she might make during the delivery.

As the labor pain increased, deputies said Goodson took a pair of scissors to "pry the baby out."

The infant, a 9.5-pound, 20.4-inch boy, was delivered alive and in the toilet, detectives said.

Goodson lifted the moving infant from the toilet, felt for a pulse, found one, and then placed her hands around the infant's neck and squeezed until he wasn't moving or breathing, deputies said.

Investigators said she then cleaned up the bathroom and bathed herself and the dead infant, before placing him in a shoebox, along with soiled towels and clothing.

Detectives said Goodson, who weighs 100 pounds and is approximately 5-feet-3-inches-tall, had been attempting to conceal her pregnancy from her family by wearing baggy clothing for the past several months.

According to an autopsy report, the boy was a full-term infant and he was alive and breathing prior to death. The cause of death was a result of asphyxia from strangulation and blunt force trauma, said the report.

Goodson told detectives she choked the baby to "stop him from breathing."

Investigators said she was medically screened and cleared prior to being arrested and transported to the Polk County Juvenile Detention Facility.