Here’s what caused the massive, fiery I-84 wreck that sent 4 to the hospital

Interstate 84 reopened fully in Boise on Tuesday evening, but Idaho State Police are still investigating an early morning crash that engulfed a tractor-trailer carrying lumber in flames, damaged nine vehicles, delayed traffic for most of the day and hospitalized one woman in life-threatening condition.

All lanes of I-84 near the Cloverdale Road overpass reopened at around 5:25 p.m. on Tuesday, according to a tweet from the Idaho State Police.

Four people were hospitalized: three men with minor injuries and a 27-year-old Boise woman with serious injuries, according to a news release. The crash blocked all eight lanes of I-84 for hours on Tuesday, and two lanes in either direction still were closed until the full reopening.

ISP said the crash occurred at 7:34 a.m. when an eastbound Toyota pickup truck changed lanes quickly, hitting a semitrailer hauling 65,000 pounds of lumber. The semi veered out of its lane and struck a white pickup before breaking through the concrete median and hitting a westbound tractor-trailer, whose cab swung around and “jack-knifed,” according to ISP.

Debris from one of the semis “hit the roof of a westbound Toyota Camry,” according to the release, knocking the 27-year-old woman who was driving unconscious while her vehicle kept moving. The semi hauling lumber caught fire, and wreckage from the crash extended into nearly every lane of traffic.

The drivers of the red and white pickups, a 28-year-old Parma man and a 40-year-old Nampa man, respectively, were hospitalized, as was the 28-year-old Boise man who was driving the semitrailer that ignited.

Boise and Meridian police, the Ada County Sheriff’s Office, Ada County EMS, the Boise and Meridian fire departments and the Idaho Transportation Department were all involved in the response, according to ISP.