The FBI and other local law enforcement began the search in the national forest Saturday. Petito visited the area on Aug 27.
Local news helicopters are broadcasting images of a white tent set up in a remote area, surrounded by investigators as well as search teams with horses.
Petito is one of three people missing near Grand Teton Park this summer.
A deputy coroner arrived at the Moran Vista campsite in the national forest around 2 p.m. MST. Vehicles carrying search dogs left shortly after.
Police were letting vehicles out of the dispersed camping area but turned away new arrivals at the entrance on Spread Creek Rd.
Petito and her 23-year-old fiancé, Brian Laundrie, were traveling from New York to Oregon in a white 2012 Ford Transit, which was spotted near Spread Creek in late August.
Petito’s family reported her missing on Sept. 11, weeks after she last spoke with her mother in late August.