Satyavathi Venna arrived in the United States in July for a visit and was set to return home in January. The family was living together in the apartment.
FBI agents handed out 200 flyers at the Marquis apartment's guard shack early Tuesday morning in hope someone would come forward with information into the disappearance of Saavni Venna.
Montgomery County detectives were stopping cars in and out of the complex's parking lot asking drivers questions and handing out a Missing Child flyer.
Pennsylvania State Police issued an Amber Alert at 4:19 p.m. Monday for the girl, described as Asian Indian infant who weighs 21 pounds and has black hair and brown eyes. She was wearing jewelry and a white dress with pink flowers.
Authorities said the baby was last seen between 8 a.m. and 1 p.m. Monday at the Marquis apartments, on the 200 block of West DeKalb Pike.
In a televised news conference late Monday night, 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."
Friends and family of Saavni gathered Tuesday morning inside the township building by the police department. Her parents had been at police station overnight.
The family is from Andhra Pradesh, India, according to Venkata Venna's Facebook page.
Both the girl's parents are software engineers, friends say.
Indeed, Saavni's abduction and her gradmother's killing have hit close to home for Veronica Nava, 36, who lives in the A building. The mother of two, and pregnant with a third, first heard of the incident around 2 p.m. yesterday while doing laundry.
"You always fear the worst," she said. "A homicide is a big shock."
The Marquis complex has five buildings. Tenants say it has a good price point, with a three bedroom apartment renting for $1,200. The murder occurred on the 6th floor of building C, which has 11 floors. The complex was built in the 1950s and needs updating they said.
"I feel bad ... for the guy who is looking for his daughter," said resident Tanya Bazylskiy, 37, who lives in building C. She said the apartment has many young professionals and families living there. "Good neighbors."
Many older grandparents watch their grandchildren at the complex, Bazylskiy said.
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."
The Montgomery County District Attorney's Office has given no details of the abduction, citing concern for the child's safety.
The FBI said it was assisting in the investigation.
Police said that anyone with information should call 610-265-3232.
Contact Carolyn Davis at 610-313-8109, email@example.com, or @carolyntweets on Twitter.
Inquirer staff writer Jennifer Lin contributed to this article.