Dr. Brent Blue said the cause of death was strangulation and the manner was homicide.
The 22-year-old Long Island native was killed three or four weeks before her body was found on Sept. 19, Blue said.
Petito was last seen with boyfriend Brian Laundrie, 23, who was identified as a person of interest when he returned home in Petito's van without her.
Authorities issued a warrant for Landrie's arrest after he apparently used Petito's debit card after her death.
This is a developing story. Check back for more.
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