Flags at half-staff to mark I-35W Bridge collapse anniversary

It's been 10 years since the Interstate 35W Bridge collapsed during rush hour, killing more than a dozen people. 

To mark the anniversary, Gov. Mark Dayton ordered all U.S. and Minnesota flags to be flown at half-staff at state and federal buildings across Minnesota from sunrise to sunset on Tuesday. 

“We must never forget the terrible losses and injuries, which so many Minnesotans suffered on that tragic day and have endured every day thereafter,” Dayton said in a statement. 

The eight-lane bridge collapsed into the Mississippi River in downtown Minneapolis at 6:05 p.m. on Aug. 1, 2007, the National Transportation Safety Board (NTSB) said. 

There were 111 vehicles on the part of the bridge that collapsed, sending motorists and construction equipment tumbling into the river below.

Thirteen people were killed and another 145 others were injured. 

Dayton's proclamation aims to remember the victims, support those affected by the collapse, and thank first responders. 

The NTSB said the likely cause of the collapse was "inadequate load capacity" due to a design mistake. The gusset plates on the bridge failed due to a combination of more weight on the bridge due to pervious bridge modifications, as well as "traffic and concentrated construction loads" on the bridge that day. 

You can read the NTSB's full report here. 

The collapse helped change the way people looked at the safety of bridges across Minnesota. Read more about that in this story by MPR News.