Cortland county investigators say a mechanical failure is the cause of a crash that killed seven people in the town of Truxton last week.

The accident happened just before 6 p.m. Wednesday on Route 13 after a tractor trailer heading south lost its trailer, which crashed into a minivan headed in the opposite direction.

Investigators said the trailer disconnected because the fifth wheel locking mechanism failed on the tractor trailer.

Among the fatalities were four children ranging from 4-7 years old. The investigation is ongoing and no tickets have been issued as yet.