A four-alarm warehouse fire broke at San Francisco’s Pier 45 on Saturday morning, prompting a response of over 150 firefighters. According to information provided by the San Francisco Fire Department, around one-quarter of the Fisherman’s Wharf pier has been consumed by the fire while the warehouse was completely destroyed.

Photos made their way online showing the massive flames in the small hours of the morning. The fire was first called in at 4:17 a.m. local time. The pier has since been fully evacuated while firefighters work to contain the fire, and some nearby businesses still operating were cleared out, as well.

“When firefighters arrived, the flames were literally lapping over the Jeremiah O'Brien,” Lt. Jonathan Baxter told San Francisco CBS affiliate KPIX, referring to a famed WWII-era warship docked at the pier. “They literally saved the O'Brien.”

The St. Francis fireboat was able to get into position and protect the antique ship from the blaze. Several other fireboats are in position around the pier helping to bring the fire under control.

Only one firefighter has been injured, with just a cut to his hand. He was taken to a local hospital and is expected to make a full recovery. A fire engine was also reportedly damaged.

The warehouse where the blaze started housed a large fish processing plant operated by Caito Fisheries. It is unknown at this time if anyone was inside the building when the fire started or when it collapsed, though it was known to be frequented by homeless people.

As responders fight to keep the flames from spreading to more buildings on the pier, investigators have begun using security footage to try and determine what started the fire.

The Golden Gate Bridge in San Francisco, California, is a popular stop on many US road trips The Golden Gate Bridge in San Francisco, California, is a popular stop on many US road trips Photo: GETTY IMAGES NORTH AMERICA / JUSTIN SULLIVAN