Truck that caught fire, exploded on I-5 in Seattle was carrying oxygen, propane and more

SEATTLE - The southbound lanes of Interstate 5 shut down Thursday afternoon in Downtown Seattle after a welding vehicle caught fire and began exploding. After an hours-long shutdown, the freeway reopened.

According to the Seattle Fire Department, no injuries were reported. It was too soon to know what caused the fire, but officials said they suspected a possible maintenance issue with the truck itself.

All lanes were closed around 1:30 p.m. between Mercer and State Route 520. At around 2:30 p.m., the northbound lanes reopened.

The Express Lanes were closed for several hours but have since reopened to allow southbound traffic to get through Downtown Seattle.

Authorities said Friday that it was a welding truck carrying oxygen, acetylene, propane and an argon cylinder that caught fire. Explosions could be seen for at least 30 minutes.

Just before 4:30 p.m., firefighters said the fire was extinguished.

Officials warned residents living near I-5 at Lakeview Blvd. E to close their windows and doors to avoid getting toxic smoke exposure from the fire.

The Mercer Street exit sign was charred and burned and had to be taken down. 

The pavement was also damaged, but it was deemed safe enough for drivers to use. 

"We had a little bit of a concrete kind of burn and it's called the laminating work. Just kind of a layer comes loose and so we need to put some asphalt on that as a temporary patch and then we will come back later on a scheduled evening to make a more permanent fix," said Tom Pearce, a spokesperson for the Washington State Department of Transportation. 

But this was only a temporary fix– WSDOT says some of the concrete might have come loose and work will be scheduled for a more permanent fix.

Pearce said this will happen in the middle of the night when it affects fewer people.

Editor's note: An earlier version of this story said the tanks contained liquid oxygen as first reported by the Seattle Fire Department. On Friday, the department issued a correction stating that "The truck that caught fire was a welding supply delivery truck carrying oxygen, acetylene and propane, plus an argon cylinder. The oxygen was not liquid." The story has been updated.