NEW YORK (CBSNewYork) – Police arrested a man Monday in connection to a 7-alarm fire that ripped through a parking garage in Brooklyn.

21 people, including three civilians and 18 firefighters, were injured in the blaze FDNY sources believe was intentionally set by 23-year-old Avon Stephens.

The fire broke out at around 9 a.m., destroying multiple cars at the King’s Plaza Shopping Center in Mill Basin. Police say a man was seen leaving the garage right before the fire, adding that an accelerant was likely used judging by how quickly the flames spread.

“Units responded and found there to be multiple cars being stored here by a local car dealer, perhaps as many as 120. We’re not sure yet how many of them burned, but many of these cars were involved in this fire,” FDNY Commissioner Daniel Nigro said.

Some 250-300 firefighters responded to the blaze.

The garage is being checked for possible structural damage, Nigro said.

At the peak of the blaze, plumes of smoke could be seen pouring from the structure, and officials issued a warning to people with heart or lung conditions such as asthma to avoid the area, stay indoors and keep windows closed due to smoke.

Stores in the shopping mall typically open at 10 a.m., so few customers were at the scene when emergency crews responded to the initial call. Stores remain closed as firefighters continue to battle the blaze.

Kings Plaza mall shut down as the fire and smoke spread. It announced it would remain shut for the day in the aftermath of the fire.

Witnesses reported hearing several explosions during the fire.

“I just heard a loud explosion, and I looked, and then after that, it’s like you heard another explosion,” said Benshley Francillion. “A few minutes after you seen a whole bunch a smoke coming out. Then it had popped up and I started recording and stuff, because it was, like, crazy.”

“Any time you have a car fire, you’re likely to have certainly tires explode,” Nigro said. “And much of what they heard were tires on these multiple vehicles exploding many times. Very dangerous for our members, and for anybody nearby.”

The heat, confined space, and toxic smoke all combined to make it a very challenging fire to fight, Nigro added. Police say the suspect they’re looking for might have had some type of disagreement with the car dealer who owned the majority of the charred vehicles.

Thankfully, none of the injuries were life threatening. Sources say Stephens is facing federal arson charges, with damage to the parking lot and automobiles expected to cost in the millions of dollars.

Anyone with information in regards to this incident is asked to call the NYPD’s Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74682). The public can also submit their tips by logging onto the Crime stoppers website at WWW.NYPDCRIMESTOPPERS.COM or by texting their tips to 274637 (CRIMES) then enter TIP577.