CHINO HILLS (CBSLA) — At least two people were killed in a pileup involving a box truck and five other vehicles on the southbound 71 Freeway at Butterfield Ranch Road in Chino Hills Wednesday.

The chain reaction crash at about 8:15 a.m. started with a box truck that could not or simply did not slow down as traffic slowed in front of him on the southbound 71 Freeway at Butterfield Ranch Road. From the initial investigation, authorities say the truck first hit one car and pushed it out of the way, then hit a second car, killing two people inside and severely injuring a 15-year-old.

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The truck then lost control, spun across lanes and overturned onto a car and pinned another against the guard rail.

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Two people were pronounced dead at the scene. A total of five people were hospitalized, including the 15-year-old who was in critical condition.

Drivers familiar with the area know that the 71 Freeway loses lanes as it goes south from Los Angeles County into San Bernardino County. It’s not clear if a slowdown due to the loss of lanes is what led to the crash.

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Traffic was diverted off the freeway at Pine and the southbound lanes were shut down at Butterfield Ranch Road for several hours.