katharine is at the scene. what are they looking for? >> they are not exactly sure where it slammed into the structure. it's possible i suppose that the structure was on its way to collapsing and fell on that rig. perhaps it was its weight and not the impact. there is a lot they have to tease out of this. there were transportation engineers swarming over the bridge last night and the state has emergency repair crews on call, but all of that will have to wait for national transportation safety board investigators who are on their way here, expected to arrive before midday, local time to try and find out exactly what happened last night at 7:00 p.m. a dramatic scene north of seattle. two vehicles crossing the i-5 bridge when it collapsed. three people inside those cars were tossed into the skagit river. fortunately, rescue teams arrived quickly. plucking them from the fast-moving waters. this man was on the bridge when it folded. >> a big puff of dust, and i hit