NB I-5 blocked at Nisqually River Bridge due to deadly vehicle fire

THURSTON COUNTY, Wash. - Northbound I-5 traffic is fully blocked at the Nisqually River Bridge due to a deadly vehicle fire.
What we know:
All lanes of northbound I-5 are currently being diverted to Nisqually exit 114. There is no estimated time for reopening.
What they're saying:
Washington State Patrol initially said there was a vehicle explosion, but later confirmed that a "mechanical mishap" had occurred involving two vehicles.
One of the vehicles caught on fire, and at least one person died, according to Washington State Patrol.
Drivers are asked to seek alternate routes and expect delays. Updates can be found on the WSDOT website.
What we don't know:
It's currently unknown what caused the mechanical mishap or the fatality.
This is a developing story. Check back for updates.
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The Source: Information in this story came from Washington State Patrol District 1 Public Information Officer Kameron Watts and the Washington State Department of Transportation.