National Transportation Safety Board Chairwoman Jennifer Homendy revealed details about the tragedy at a news conference on Monday, calling the scene of Sunday's crash "utter devastation".
She didn't say how many people were in the SUV or where the dead were located.
Homendy walked the route the Boeing 767 followed, noting tyre marks from the pavement into the grass, the destroyed van carrying the cleaning crew, torn fencing, navigational equipment, and the crushed SUV outside airport property.
The debris included vehicle air bags, equipment from the vehicles, the airplane and the airport, and "fencing everywhere", Homendy said.
"It's pretty extensive. Hard to see and I'm sure it must have been very difficult for the responders as well," Homendy said.
The plane travelled about 400 metres past the paved surface. Debris was everywhere, she said.
"I would describe it in one word as devastating, utter devastation," Homendy said.
The van with seven people inside was "torn apart. It certainly must have been devastating," she said. The van was owned by Professional Ocean Service Corp., an airline cleaning contractor.
Homendy said the NTSB would issue more information on Tuesday, including possibly information on speed that is confirmed by the flight data recorder.
Federal investigators examining the crash spent Monday determining whether the plane touched down too late to stop safely.
Video of Sunday's landing appears to show the Boeing 767 remaining airborne well down the runway before touching down. Aviation experts said investigators will seek to determine exactly where the plane landed, whether it was beyond the normal touchdown zone, and why the pilots did not abandon the landing.
Investigators will also examine the plane's speed and braking, weather and wind conditions, the aircraft's mechanical condition and other factors that could have contributed to the deadly overrun.Â
