Transcript for Deadly Highway Bridge Collapse in Salado, Texas
We're going to turn next tonight to the breaking news in Texas. The deadly bridge collapse on interstate 35. A tractor trailer under that debris, it had rammed an overpass. Sending beams hurtling down on unsuspecting drivers. ABC's Ryan Owens at the crash site in Texas. Reporter: We've all seen them. Loaded semis that look too big to make it under an interstate overpass. Investigators think that's exactly what happened this morning, along interstate 35 between Dallas and Austin. A semi that police think was speeding slammed into a beam on this overpass under construction. The impact so devastating, it caused other beams to come crashing down. One of them landed on a man in a pickup truck. He was killed. Three others injured. One of the 18 wheelers had some equipment on the top of the trailer, ran into the bridge itself, at that point, two of the pillars from the other side fell off and struck a vehicle that was heading the opposite direction. Reporter: Three signs posted two miles before the overpass warn of its height. Authorities are investigating why the truck driver seemed to have ignored them. We're looking at the driver, we're looking at the truck itself and also the roadway. Reporter: Tonight, crews are cleaning up smashed cars and debris. This incredibly busy interstate has been closed since 11:00 this morning and will remain that way for several more hours. Ryan Owens, ABC news, Texas. Ryan, thank you.
This transcript has been automatically generated and may not be 100% accurate.