OAKLAND — Unable to determine how two train cars jumped the tracks near Daly City on Saturday, BART has hired a Colorado consulting firm to help solve the mystery, a BART spokesman said Wednesday.

Pueblo, Colorado-based Transportation Technology Center, Inc., will look into what factors contributed to the puzzling derailment, which somehow affected only two cars in the middle of a nine-car train, BART spokesman Jim Allison said.

The train was carrying two dozen people just before 3 p.m. Saturday, when somehow, the two middle cars landed several feet from the tracks. All the passengers and employees disembarked without injury, BART officials said.

On Monday, BART spokeswoman Alicia Trost said workers had been able to pinpoint the location of the derailment: a rail-joint, which mechanically joins two sections of track, placed some 400 feet from the Daly City station.

That may explain the “how” but not the “why,” and for that, Allison said Transportation Technology Center will examine other contributing causes to the crash, such as the wheels.

“Given the fact that multiple trains had made the exact same crossover move and successfully passed over the same section of track on Saturday prior to the derailment, (the consultant) will also look at the wheels of the car,” he said. “Early indications are that multiple factors were involved in the derailment.”