Two freight trucks headed for Harbor Island collided as one cut the other off around 2pm according to the drivers, in the 1000 block of Spokane Street, just as it emerges from under the overpass. A fuel tank on the truck that was cut off was struck and leaking fuel on to the roadway. 

That resulted in a HazMat response from the Seattle Fire Department and stopped all eastbound traffic at that point. Since the bridge is closed to all non essential traffic this affected only commercial traffic. But the back up extended out to 1st Ave South and beyond as the had to wait for the fuel to basically drain out, since no way to catch it was possible.