The infant was found on a doorstep of a home in the 3000 block of Channing Street NE about 11 p.m. on Jan. 15. She was stiff and bleeding from the nose and mouth, and bundled in a striped towel.
Authorities pronounced the baby dead hours later.
Police describe the girl as African American and 1 month old or younger.
The cause of death has not been determined as investigators wait for an autopsy report.
Anyone with information about the abandoned girl or her parents can send an anonymous text message to 50411 or call 202-727-9099.