State transportation officials continue their investigation into the cause of a fatal tanker explosion in Frederick this weekend. The truck overturned after hitting a tree on U.S. 15 Saturday afternoon and exploded in a fireball near a residential area. At least five vehicles and six homes were damaged by the fire near Rosemont Avenue, and the driver of the tanker was pronounced dead at the scene. No other injuries have been reported. Both sides of the highway were shut down and over 100 firefighters were called to the scene. Officials are still investigating what kind of flammable liquid was in the tanker.