JERSEY CITY - Officials say at least 25 firefighters were injured battling a quick-moving fire and an explosion in Jersey City.

The four-alarm fire broke out in a three-story house on Boyd Avenue near John F. Kennedy Boulevard West shortly after 1 p.m. The fire spread to an adjacent building.

Firefighters from all over the city were called in to help fight the blaze as temperatures climbed into the upper 90s. Heat index values in Jersey City reached 112 degrees.

"This is the weather that makes my older guys retire," says Jersey City Deputy Fire Chief Kevin Stewart. "This is brutal on my guys."

One firefighter, who suffered an ankle injury, and the others, who suffered from heat-related symptoms, were all taken to Jersey City Medical Center. Their conditions are unclear, but officials say many had to be treated on scene as they waited for ambulances.

Jersey City Mayor Stephen Fulop says while the investigation is just beginning, it appears the fire started in the basement of the duplex.

In total, the fire displaced three families.