ORLANDO, Fla. (AP) — Lab tests confirmed a decomposing body had been in the trunk of a car driven by a missing girl's mother, and investigators believe the 3-year-old is dead, the sheriff's office said Monday.

Investigators have called Casey Anthony, 22, a "person of interest" in Caylee Anthony's disappearance. She faces charges of child neglect, obstruction and making false statements in the case.

"(FBI) laboratory evidence, along with additional evidence that has not been made public, leads investigators to the belief there is a strong probability that Caylee is deceased," the Orange County Sheriff's Office said. "If any evidence to the contrary is provided, it will be vigorously pursued."