Dulce Maria Alavez disappeared Sept. 16 from a playground at Bridgeton City Park. The girl and her 3-year-old brother were playing while their mother sat in her car with an 8-year-old relative.
The mother told police her son soon ran back to the car crying and pointed to the area where he last saw his sister. They looked but could not locate her.
EXPLAINED:What are the criteria for issuing an Amber Alert?
An Amber Alert was issued the following day. Authorities believe the girl was taken by a man who led her to a red van.
Surveillance video shows Dulce with her family, picking out ice cream from a store's freezer, right before she was taken in broad daylight last Monday.
WATCH: Last images of Dulce Maria Alavez before she went missing
Investigators said an unidentified man may have lured Dulce into a red van with tinted windows.
"I went looking for her and I asked people and I couldn't find nothing," said Dulce's mother Noema Alavez Perez.
Her mother telling police she was sitting in a car 30 yards away when her daughter disappeared.
"All of us are missing her a lot," she said. "Everyone is worried about her."
WATCH: The family of Dulce Maria Alavez issued a plea
Late Monday afternoon, authorities were back at the park where Dulce vanished hoping to find more clues.
Authorities are asking anyone who may have photos or videos and was near the park last week to upload them to the FBI by CLICKING HERE.
-- The Associated Press contributed to this report.