UPDATE: Delaware State Police have released details about what caused the fatal crash that closed northbound and southbound I-495 in Claymont for several hours Saturday

UPDATE Aug. 12, 11:53 a.m.:

The Delaware State Police Collision Reconstruction Unit is investigating a fatal crash involving an overturned tractor trailer that happened at about 3:02 a.m., Saturday, Aug. 11 on I-495 northbound just south of the Philadelphia Pike in Claymont.

The initial investigation has determined that a 2014 Toyota Avalon had become disabled and was partially blocking the right lane of I-495 northbound, about a quarter-mile south of the Philadelphia Pike off-ramp.

A 1998 Buick Le Sabre, driven by a 27-year-old Philadelphia woman, was traveling north on I-495 in the right lane when she saw the disabled vehicle and swerved left to avoid a collision, but could not do so. The right side of the Buick struck the left side of the Toyota.

The Toyota remained disabled in the right lane.

A 53-year-old Newark man was driving north in a 2018 Volvo tanker truck and couldn't stop in time to avoid a collision with the disabled vehicle in the right lane. The front of his truck hit the rear of the Toyota, and the truck turned on its side and slid. The cab portion of the Volvo struck a guard rail before the truck stopped.

The driver of the Volvo tanker truck, who was properly restrained, was pronounced deceased at the scene, police said. Identification is pending next of kin notification.

The collision with the truck pushed the Toyota off the right side of the road where it struck a guardrail and then rolled down an embankment before stopping.

The driver of the Toyota, a 46-year-old Philadelphia man, had exited the car when it became disabled. He wasn't injured.

The woman driving the Buick brought her car to a controlled stop and remained at the scene. She was properly restrained and wasn't injured, police said.

The tanker truck was carrying molten sulfur. There was no leakage, but the road was closed for about 11 hours while the scene was investigated and cleared.

The investigation is continuing and police are asking anyone with information to call Cpl. Forester of the Troop 2 Collision Reconstruction Unit at (302) 365-8485.

Information may also be provided by calling Delaware Crime Stoppers at 1-800-TIP-3333 or on the internet at http://www.delaware.crimestoppersweb.com

UPDATE Aug. 11, 2:38 p.m.:

Both northbound and southbound I-495 have reopened as of 2:38 p.m., according to Delaware State Police.

UPDATE Aug. 11, 12:50 p.m.:

Northbound I-495 has reopened in Claymont but southbound I-495 remains closed as of 12:50 p.m., according to Delaware State Police.

ORIGINAL REPORT Aug. 11:

Delaware State Police are investigating a fatal crash involving an overturned tractor trailer that occurred at 3:02 a.m. today, Saturday, Aug. 11, on I-495 northbound just south of Philadelphia Pike in Claymont.

As a result of the crash, I-495 northbound was closed between Edgemoor Road and Philadelphia Pike, and I-495 southbound was closed between Edgemoor Road and the Pennsylvania state line.

Police said they anticipate the road being closed for an extended period of time. There is no projected time for the re-opening at this point as the investigation and clean-up operation continue.

For updated road closure information click on the following link:

http://www.deldot.gov/Traffic/travel_advisory/index.shtml#advisories.

The investigation is in the early stages and more details will be released as they become available, police said.