The fire forced the closure of southbound I-5 near Mercer Street for hours on July 28, 2022.
According to preliminary information from Seattle Fire, the fire originated from the undercarriage of the truck due to a mechanical failure. That fire may have spread to the flat bed and tanks.
https://www.king5.com/article/traffic/i-5-1-lane-mercer-truck-fire/281-598deb5e-a57b-4af2-bcab-358fece9082d