Saanvi Venna has been missing since her 61-year-old grandmother, Satyavathi Venna, was killed inside the King of Prussia apartment while baby-sitting. Investigators believe the abduction happened between 8 a.m. and 1 p.m. Monday.
Police have been searching the apartment complex and surrounding area. Law enforcement and community groups are offering a $30,000 reward.
The Philadelphia Inquirer says more than 200 people attended a candlelight vigil at a King of Prussia park on Wednesday night at which relatives prayed and pleaded for the girl's safe return.
Prasad Sanikommu, a cousin of the child's father, said "We hope that Saanvi is returned so we can all celebrate her birthday . . . together." Before disbanding, participants joined in a prayer in the Telugu language that was translated as "Take me from darkness to light, from ignorance to bliss, and give me peace."
Upper Merion Township police say the girl's father and mother immigrated to the U.S. from India in February 2007 and moved to the apartment in June.
The grandmother arrived in July and was scheduled to return home in January.