Eight fire engines were called to a block of flats in Newmarket after fireworks were set off inside.
Alarms were triggered by smoke coming from the fireworks, which had been set off deliberately in a stairwell of the building, in Icewell Hill, shortly before 9pm on Saturday.
Crews from Newmarket, Mildenhall, Wickhambrook, Burwell, Soham, Cambridge and Ixworth attended the scene for more than two hours.
Police were also called to the scene due to the nature of the fire.
A Suffolk Police spokesman said police were making inquiries into the incident.