Pet ferrets bite off newborn baby's nose and maul face after escaping from cage

Police officer said mauling is 'the worst case I have ever seen in 45 years'

The mother was alerted to the incident when she heard the baby screaming and ran down the stairs, causing the ferrets to scarper (Getty Images)

Three ferrets attacked a month-old baby who had been left alone in a car seat and bit off her nose, part of her cheek and lip, authorities in the US say.

Officials in Darby, Pennsylvania, say the baby was mauled by the animals when they escaped from a cloth cage while both parents were upstairs in the family home.

The mother was alerted to the incident when she heard the baby screaming and ran down the stairs, causing the ferrets to scarper. The father’s child was reportedly asleep at the time.

Police who attended the scene said the mother had left the baby in a car seat on the floor of the dining room.

Four other young children, all under the age of five, are currently being cared for by relatives.

The only food besides animal food found in the house was "peanut butter and cranberries", investigators said.

Police Chief Robert Smythe told the Delaware County Daily Times the case was the worst case he has seen in 45 years of policing.

"Just imagine that 1-month-old baby, that can't help herself, (and) two or three animals are eating it alive," he added. "Imagine the pain."

The child is in a stable condition in intensive care after undergoing emergency reconstructive surgery at Children's Hospital of Philadelphia.