Investigators say a 3-year-old boy playing with a stove burner caused New York City's worst fire in 25 years.

Twelve people were killed in Thursday night's fire in the Bronx, including four young children.

Authorities say the boy, who lived on the first floor of the building, had a history of playing with stove burners.

But there's a way that parents can child-proof their stoves. 

You remove the knob on the stove and install a plastic cover that prevents a child from having access to flames. The covers are under $10 and could prevent a tragedy like the deadly fire in New York City.  

At the Morris County Public Safety Training Academy in New Jersey, Inside Edition was given a demonstration of what it takes to battle such a monumental blaze.

Authorities say to close the doors behind you as you exit a burning building. 

“The door is hot in the middle, I know the fire has progressed to this side of the room,” Scott Warner, a Morris County firefighter, told Inside Edition. 

Firefighters say the blaze is also a reminder to change your smoke alarm batteries. Warner says there should be smoke detectors in the common area of the house and in the bedroom.

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