The FBI has set up a special hotline for people to call with any information: 1-800-CALL-FBI or 1-800-225-5324.
The family of the girl is offering a $6,000 reward.
Worried family members handed out fliers Thursday as they continued to search for the missing toddler from northwest Indiana.
The FBI said that surveillance video inside the gas station shows the babysitter in the gas station at the time she said she was there. But there are not cameras outside the gas station, so there is no way of telling whether Jada was actually in that car.
Meantime, Jada's parents have gotten very little sleep since Tuesday night, as they continue their search.
Melissa Swiontek came back to the gas station, with the hope that someone may return Jada there.
"I just want her to just walk back over here. I keep thinking she'll be back here," said Swiontek.
While police and the FBI continue their investigation, Swiontek and Jada's father, Clarence Justice, have spent all of their waking hours trying to give Jada's picture to as many people as possible.
"Today I'm continuing with the search of my daughter, handing out fliers, talking to whoever in the neighborhood, whoever is willing to listen," said Justice.
Jada Justice is going to be 3 in August. This week her mother placed her in the care of her 18-year-old cousin, Anjelica Castillo, while Melissa Swiontek planned an out of town trip. She says she's taken care of her children several times before and is a good babysitter.
"I definitely trusted her, and Jada was so happy to go with her. She knows she has a playhouse for her at home," said Swiontek.
But even Swiontek questions Castillo's story that she told police. Castillo said she drove a couple of blocks from her home to a Gary gas station to buy milk on Tuesday night. She says she left Jada in the car with the doors unlocked when she went inside. When she came out, Jada was gone.
"It doesn't make sense. It's not her to do something so stupid like that, to leave her in there in this area," said Swiontek.
"I don't believe her one bit. I don't believe it," said Clarence Justice. "Because it don't all add up."
Jada's parents say it all doesn't add up or make sense because Anjelica Castillo told police that she parked her car right on the side of the gas station in the pouring rain, nowhere near the front door.
Families say as of Wednesday night, Castillo was in police custody facing questioning and child endangerment charges.
Anyone with information should call 1-800 225-5324 or 1-800-CALL-FBI.
Authorities suspicious of sitter's version
Authorities say they are suspicious of the sitter's version of the chain of events, as are some of her relatives.
"She was involved a long time ago with gangs and a lot of drugs. She stole. She was bad. She has got better. She has never done anything like this to our family. She loves our family. She loves those kids," said Alyssa Huerta, Jada's aunt.
Police have also questioned the babysitter's boyfriend after they learned he had suffered some severe burns recently.
Jada Justice is of average height and weight of a girl her age. She is of African American and Hispanic descent and has dark hair and dark eyes and was last seen wearing a white tank top with orange and green stripes and white sandals.
"If anybody has my child, drop her off at a fire station, library. Drop her off somewhere that somebody could locate her. They could report her back to the police, so she could come back to us," said Clarence Justice.