Texas authorities told The Arizona Republic that a truck carrying used clothing from Phoenix arrived at a warehouse in McAllen Wednesday evening.
The truck's trailer was unloaded the next day by employees at the warehouse. As they were sorting through boxes of used clothes, employees say they found the remains of the baby inside a cardboard box, stuffed between garments.
The girl hasn't been identified.
Phoenix police spokesman Sgt. Steve Martos says investigators are waiting to hear from officials in Texas who are conducting an autopsy to determine whether the baby was born alive or stillborn.
Information from: The Arizona Republic