Fog Blog U.S. News Log: Phoenix Train Bridge Disaster:

Investigators are still working to determine how a freight train derailed on a bridge over Tempe Town Lake on Wednesday, sparking a massive fire and causing the bridge to partially collapse. The fire was pumping thick black smoke into the air. That smoke plume was visible for miles.

Tim McMahan, a spokesman for Union Pacific Railroad, said as many as 10 train cars derailed at about 6:15 a.m. The south side of the bridge then collapsed and caught fire. A spokesman said the train crew was not hurt but one person at the park was treated for smoke inhalation. The City of Tempe said a firefighter was treated and released after being overwhelmed because of the heat.