Liam Levender-Lewis was last seen in the 3500 block of Warder Street on Sept. 19 at 5 p.m., according to the Metropolitan Police Department.
The infant was described as a black boy, with brown eyes and black hair, and weighing between 11 and 12 pounds, officials reported.
Before he went missing, Levander-Lewis was wearing a blue onesie with dinosaurs on it, authorities said.
Anyone with information on the child's whereabouts should contact police at 202-727-9099.
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