The video appeared on YouTube.com before being removed and is on other Web sites.
The young women told an investigator that they got bored during a return trip from Padre Island and were playing with the little girl, who was following instructions to roll her eyes back, said Lt. John Martin, a spokesman with the Harris County Sheriff's Office.
The video, which runs 2 minutes, 28 seconds, was taken in a van and shows a girl who appears to be about 2 years old. As the young women tease her, the toddler rolls her eyes back until only the whites show.
Some of the women can be heard laughing and seeming to suggest that Ecstasy might be responsible for the child's behavior. It also shows an infant being handed around in the back seat.
"Cookie, stop rolling, girl. ... You shouldn't have popped no X," says one of the young women, as she squeezes the little girl's cheeks and taps her on her head, telling her to stop rolling her eyes. "X" is a slang term for Ecstasy.
In addition to the two children, there were seven people in the van — the toddler's 21-year-old mother, two other adults and four teenage girls under 17, he said. All are from Houston, and no charges have been filed.
Area authorities became involved after clues in the video indicated it had been filmed in Texas. A map of Jackson County can be seen in the video, and an announcer for a Christian radio station in Houston can be heard in the background.