SAN ANTONIO - The FBI is joining in the search for a 3-year-old girl who went missing from a Texas playground on Monday.

Lina Sadar Khil was last seen Dec. 20 at a San Antonio playground Monday evening between 4 p.m. and 5 p.m., according to the San Antonio Police Department. Authorities report she was with her mother, who left her alone for an unknown amount of time. When her mother returned, Lina was nowhere to be found.

Authorities told ABC News there is no indication that Lina is with a family member and say the toddler may be in "grave, immediate danger."

Police say she was wearing a black jacket, red dress and black shoes at the time of her disappearance.

The SAPD asks that anyone with information on the case contacts their Missing Person's Unit at 210-207-7660.