A fireworks explosion on a deck injured nine people in New Hampshire and left two toddlers severely injured in an accident one neighbor said "sounded like a million gunshots."
Five people were taken to the hospital by ambulance, while two children ages 3 and 4, who were described as "severe" were taken by helicopter for treatment in Boston.
One neighbor said he could feel his house shake 200 yards away during the explosion, ABC News' affiliate WMUR reported. Another neighbor likened the explosion to gun shots.
"I heard it sounded like a million gunshots, and I thought maybe they were testing it, and then I saw the huge mushroom cloud and I was like, 'Oh man, that can't be good,'" Taylor Jackson told the station.
At least 30 people were inside the Pelham, N.H. home attending a party when disaster struck.
Elsewhere in New Hampshire, police said four children were injured on Rye Beach after they put several lit sparklers inside a glass jar, causing it to explode.
Police did not release the ages or conditions of the injured, but said one was transported by helicopter to Massachusetts General Hospital late Tuesday night, while the other three were taken by ambulance to Portsmouth Regional Hospital.
A 24-year-old man is recuperating in a Florida hospital after fireworks he was handling blew off his left thumb and severely injured his hands early today, the Tampa Bay Times reported.
Matthew Lewandowski was loading a firework mortar when it exploded in the tube he was holding, blowing off his left thumb and giving him serious burns on his hands, arms, stomach and right leg, the newspaper reported.
Lewandowski's condition was not immediately known.
The dangers of fireworks are also compounded by a heat wave sweeping the nation.
Cities and counties in 20 states have banned fireworks this 4th of July due to scorching temperatures and drought conditions.
Parts of nearly a dozen states, from the southwest to the west, are in severe drought.
Thousands of square miles have been charred by wildfires in recent months. Firefighters in Colorado are currently working to contain the Waldo Canyon Fire, which burned through more than 18,000 acres after it started in June 23.
Fireworks were blamed for more than 15,500 blazes and $36 million in property damage in 2010, according to the National Fire Protection Association.
Twenty states across the U.S. are under a heat advisory today and experiencing record breaking temperatures.
Minneapolis is expected to have two 100 degree days in a row, something that has never before been recorded in the city. Memphis and Chicago will hit 101 degrees. Coupled with humidity, the triple digit temperatures will feel more like 108 to 115 degrees.