A fire early Saturday morning destroyed a fish processing and storage warehouse at San Francisco’s Fisherman’s Wharf and for a time threatened part of the popular tourist area

But firefighters saved the Jeremiah O’Brien, a World War II liberty ship.

Flames from the blaze shot more than 100 feet in air and billows of black smoke shrouded the waterfront as 150 firefighters with 50 trucks and other pieces of equipment, including fireboats, fought the fire on Pier 45, where a large warehouse known as Shed C is home to fishing and maritime businesses.

One firefighter was injured, with hand cuts. She was treated at a local hospital.

The USS Jeremiah O’Brien is also moored at the pier. Flames licked at the historic vessel but it escaped with only cosmetic damage, thanks to efforts by firefighters.

Philip O’Hara, senior shipkeeper for the O’Brien, said the ship was in great shape and “just got singed a bit.” O’Hara credited the city’s fire boat, the St. Francis, for saving the day.

“I am very grateful,” said O’Hara, who has worked on the ship for 20 years. “This ship, she’s something else. She’s been through a lot. She’s not going to be taken down by a shed fire.”

Fire Department Lt. Jonathan Baxter credited “our aggressive and quick, swift actions” with saving the O’Brien.

“If you’re looking for one positive,” he said, “saving a historic World War II vessel at the beginning of Memorial Day weekend is something we should be proud of as a community.”

The fire was contained at 11:30 a.m., Baxter said , after firefighters spent several hours spraying water on the smoldering debris from the ground and from three aeriel ladders the remaining hot spots.

The fire broke out around 4 a.m. and firefighters rushed to the scene. Although a cause for the blaze has yet to be determined, Baxter said that fire investigators are “looking at the possibility that homeless people were inside.” That investigation was expected to last several days.

A fisherman whose boat is docked at Pier 45 said that homeless people hang out in the warehouse and sometimes build fires for cooking

A number of workers were in the warehouse when the blaze broke out.

Lloyd Dizon, a sales person for Aloha Seafood, was taking orders when the fire began.

“It started like a little thing, then the whole structure started,” he said. “A few seconds later, the building started caving in.”

Other workers reported an explosion before the fire erupted.

Alejandro Arellano, who works for La Rocca Seafood, was cleaning out a fish storage locker.

“I saw a lot of smoke. A few minutes later, fire everywhere,” he said. “It was very, very scary. I’ve never seen anything like it.”

Hours after the fire broke out, about two dozen workers from the warehouse, many still wearing their yellow fish-processing aprons, gathered behind Alioto’s restaurant to watch firefighters pour water on the collapsed shed. They showed each other cell phone pictures they had taken of the fire and wondered when and how they will be going back to work.

The streets around the pier were almost paved with yellow hoses, some stretching for as many as four blocks to a hydrant at Beach and Taylor streets. Firefighters from at least a dozen trucks were spraying water on the blaze, with three ladder trucks drenching the warehouse from 50 feet above.

The first call came at 4:15 a.m. Truck 13 from the Sansome Street station in the Financial District was the first on the scene, and fast action by its crew prevented the fire from spreading, Baxter said.

The truck company nearly paid a heavy price. Flames from the blaze rolled out and singed the truck, forcing firefighters to turn their hoses on the vehicle to save it, Baxter said. The truck was slightly damaged, but no people were hurt.

The blaze was confined to the north end of the pier, well away from the Musée Mécanique and its historic arcade games and the restaurants and other businesses in the popular tourist area.

Kenny Belov, owner of TwoXSea, a sustainable seafood wholesaler in a building only about 50 feet from the warehouse, learned of the fire in a phone call from one of his employees at about 4:45 a.m. Then his plant manager sent a video taken on the loading dock facing the fire.

“Just breathtaking,” Belov said. “It was this massive blaze.”

Five of Belov’s employees were in the building at the time, he said, and they all evacuated safely. There was no damage to TwoXSea “as far as I know,” he added.

Belov estimated that hundreds of vehicles typically are parked in the warehouse, mostly a mix of employees’ cars and delivery trucks.

He acknowledged the crazy timing of the fire, atop the closure of restaurants caused by the coronavirus pandemic and shelter-in-place orders. Belov abruptly pivoted his business to home delivery, and he had several deliveries scheduled Saturday that wouldn’t be going out.

He also was worried a prolonged power outage could ruin the fish in his deep freezer.

“Not that it would ever need this, but the seafood industry didn’t need this now,” Belov said. “It’s surreal. We’ve obviously had a tough go the last couple months, with restaurants (closed). … Of all the problems in the world, this is not a big one. But it’s frustrating.”

A longtime crab and salmon commercial fisherman said he lost Dungeness crab, rock crab and shrimp pots to the blaze.

“I’m basically out of business,” since it’s unlikely he can get his gear replaced before the November crab season, said the fisherman, who only wanted to use his first name, Mike.

He estimated there are 19 fishermen with gear stored in the warehouse that was destroyed. The fishing fleet lost over 7,000 crab pots, worth about $265 each.

The offices of the Red and White Fleet, a bay tour company, also were destroyed, fire officials said.

Thick black smoke rolled over the bay from the blaze, which at its height sent flames climbing into the sky in the pre-dawn darkness. Even as firefighters brought the blaze under control, a thick pall of choking smoke hung over the waterfront.

By STEVE RUBENSTEIB & RON KROICHICK