Officials said both people on board the plane were killed in the impact. The victims' names were not released.
Federal Aviation Administration (FAA) officials said the pilot was not in communication with the traffic control center at the time of the crash.
"There's the possibility of some engine problems that led it to descend in a nosedive fashion," said James Poppe, a Ventura County Sheriff's official. "With the witness statements that we've been able to obtain initially was that the pilot was struggling to remain airborne."
Witnesses reported the plane looked like it lost power at least twice before it crashed. One witness saw the plane go down in front of him and called 911.
"As he heard the noise of the plane, the pilot struggling, [the witness] got up and as he observed the plane fall right in front of him, right onto the roadway in front of his truck," said Poppe.
Helicopter pictures of the scene showed the wings and nose of the aircraft were crumpled, with the tail section broken over the main body of the plane.
The plane is registered to Aviation Pacific, Inc., a Camarillo flight school.
FAA and National Transportation Safety Board officials suspended their investigation into the crash Thursday night due to the rain. They planned to resume the investigation at the scene on Friday, depending on the weather.