Authorities said the crash happened around 2:24 p.m. on State Route 126 and Telegraph Road. At least four vehicles, including a semitruck, were involved in the crash.
One person was reported dead, while two others were in serious condition and one in moderate condition, authorities said.
Traffic was closed in both directions in the area between Mountain View Road and the railroad tracks at the eastern edge of Fillmore.
It was unclear what caused the crash.
The investigation is ongoing.