She was taken to Birmingham Children's Hospital where she remains in a critical condition, West Midlands Police said.
The force spokesman said they are investigating how the baby came to be in the refuse area and are conducting inquiries around the tower block.
Detective Inspector John Smith, from the force Public Protection Unit, said: "We are making a number of enquiries to establish how this young baby has come to sustain her injuries, and how she came to be found in the refuse area of the flats.
"The two people who have been arrested are related to the baby and we are currently not seeking anyone else as part of our enquiries. We urge anyone who has information to help our investigation to come forward at the earliest opportunity."
Anyone with information on the incident is asked to contact the Public Protection Unit at Wolverhampton Central police station on 101.