Transcript for Explosion rocking a chemical plant near Houston

Back now with our index. The massive chemical plant explosion near Houston, smoke and flames P in Pasadena, Texas, not from where we're broadcasting. 20 injured. A blown valve causing a flash fire blamed for the explosion. To Philadelphia and a warehouse inferno. Flames consuming the entire building spreading to a nearby church. Fire officials say most of the city's firefighters were at the scene. No injuries reported. The cause is still under investigation. And first lady Melania trump is back home tonight. The white house reports she left the hospital this morning and is now resting comfortably and in high spirits. Mrs. Trump spent five days at Walter reed medical center to treat a benign kidney condition.

This transcript has been automatically generated and may not be 100% accurate.