An online video that allegedly shows teens teasing a toddler for using the drug Ecstasy while sitting on the floorboard of a moving vehicle is being investigated by local authorities hoping to find out who is responsible.In the video, which originally appeared on YouTube before it was removed, a second child, an infant, also is seen being handed from one person to another in the back seat of the car.Various clues in the video — a map and a Houston radio station broadcast — have gotten the sheriffs' departments in Harris and Jackson counties involved in the investigation. FBI spokeswoman Shauna Dunlap said her agency also is looking into the matter.