NEWARK - Authorities are working to determine the cause of a five-alarm blaze that left 45 firefighters injured yesterday in Newark.

More than 100 firefighters were called out to battle the blaze that engulfed seven buildings. Officials say the fire broke out at around 1:30 p.m. at 20th and Ferdinand streets.

According to authorities, five of the buildings were occupied at the time, leaving 18 people displaced from their homes.

The high heat and humidity made it difficult for firefighters to fight the fire. Twenty firefighters were treated for heat stroke or heat exhaustion. Another 25 were also injured and returned to continue fighting the blaze.

Fire officials say fighting the fire was made even more difficult by the lack of strong water pressure. With numerous engines pumping water, the water mains couldn't supply enough water to douse the flames.

There were no reports of injuries among residents.

Fire officials are still investigating the cause.

Click "NEXT" below your video player to see video from Chopper 12 of the fire.