Authorities said the baby last was seen between 8 a.m. and 1 p.m. Monday at the Marquis apartments, in the 200 block of West DeKalb Pike.
In a televised late-night news conference, Venkata Venna, Saavni's father, made a brief, emotional statement, pleading: "If someone finds my baby, could you please bring my baby back?"
Police Chief Tom Dolan had little to add but said, "We are working two investigations."
When asked whether Marquis residents should be worried, he said, "There is no concern with that right now."
The Montgomery County District Attorney's Office gave no details of the abduction, citing concern for the child's safety.
The FBI said it was assisting in the investigation.
The family is from Andhra Pradesh, India, according to Venkata Venna's Facebook page.
Asked about the paucity of information, District Attorney Risa Vetri Ferman said, via e-mail: "We are focused on finding Saavni right now. Nothing to report at this moment on other people."
Police said that anyone with information should call 610-265-3232.
A spokeswoman for Marquis Property Management issued a statement saying, "We are not at liberty to discuss the situation. We are cooperating with authorities during their investigation."
Contact Carolyn Davis at 610-313-8109, email@example.com, or @carolyntweets on Twitter.
Inquirer staff writer Jennifer Lin contributed to this article.