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CLAYMONT (CBS) — Officials have revealed the cause of the fatal crash involving a tractor-trailer that shut down I-495 on Saturday.

According to the Delaware State Police, the crash was caused by a disabled vehicle blocking the right lane of I-495 northbound just south of the Philadelphia Pike.

Fatal Accident Shuts Down I-495 NB, All Lanes Reopened In Wilmington

The crash happened at approximately 3:02 shortly after an earlier crash caused by that same vehicle, a Toyota Avalon, blocking the right lane.

Police say that the first accident happened when a woman, 27, swerved to avoid a collision with the broken down car. Unfortunately, she failed to do so and the right side of her Buick hit the left side of the Toyota.

She had noticed the vehicle blocking the lane too late to avoid hitting it, said police. The woman, who was properly restrained when the accident occurred, remained unharmed.

The right lane remained blocked following this initial accident and it was at this time, the tractor-trailer came traveling up the right lane.

Credit: Delaware State Police.

Failing to see the disabled Toyota, the 53-year-old truck driver hit the rear end of the car. That collision caused the tractor-trailer to overturn onto its left side where it began to slide, struck a guardrail, and then finally came to a stop.
This second collision forced the Toyota off the right side of the roadway where it also struck a guardrail before rolling down an embankment.
The driver of the disabled Toyota, a 46-year-old man from Philadelphia, had exited his vehicle when the car broke down and was also uninjured.
Unfortunately, although properly restrained, the driver of the tractor-trailer was pronounced dead at the scene.
He has not yet been identified.
Officials say that there was no leakage of the molten sulfur that the tractor-trailer was transporting; however, the roadway was closed for approximately 11 hours while the scene was investigated and cleared.
The investigation is still ongoing and anyone with information regarding this incident is asked to contact Cpl. J. Forester of the Troop 2 Collision Reconstruction Unit at 302-365-8485.