ORLAND (CBS/AP) — Accident investigators with the California Highway Patrol are reconstructing how fast a bus carrying high school students was going before its fiery collision with a FedEx truck that left 10 people dead.

The exercise was occurring Thursday along a section of Interstate 5 about 100 miles north of Sacramento.

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The bus was heading up California’s main north-south interstate last week with 44 Southern California students aboard. Their destination was Humboldt State University.

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Five students died, as did three adult chaperones and the drivers of the chartered bus and truck. Dozens escaped before the vehicles exploded into towering flames.

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Accident investigators say they will take months to determine why the truck tore through bushes in the freeway median without hitting the brakes before smashing into the bus.

Capt. Todd Morrison, the commander of CHP’s northern division investigative unit, told reporters at the scene Thursday that the simulation would take place in two phases.

The first would be a video test to determine what the vehicles’ drivers would have seen at the time of the crash.

After that, Morrison said extensive skid tests would be conducted using a 2007 FedEx Volvo truck and a 2014 bus very similar to those involved in the deadly crash.

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