Chelsea Noel was wearing a pink nightgown with a cartoon horse before she disappeared, police said.
Port St. Lucie Police spokesman Sgt. Frank Sabol said she was last seen just before 10 p.m. and as soon as her parents noticed she was gone, they immediately went outside to search for her.
The police department said Sunday that the FBI, the Florida Department of Law Enforcement, and several local departments are all taking part in the search for Noel. Bloodhounds have been deployed and helicopters.
A local resident donated the use of his drone to help in searching areas for the child, police said. That drone detected a discolored figure in a body of water near her home.
A dive team searched that pond for Noel this morning, but there was no sign of the toddler.
Police are asking nearby residents to check videos recorded by their surveillance cameras in hopes of finding any clues about the girl.
Sabol said that Chelsea is attracted to lights, so police checked around homes with holiday displays for her.
Chelsea is described as a black female, 3 feet tall and 40 pounds, with short black hair.