A fire on the USS Bonhomme Richard at a San Diego naval base has been extinguished after a four-day battle against one of the worst infernos to rip through a U.S. warship outside of combat in recent years, the Navy said Thursday.

Rear Adm. Philip E. Sobeck called the last 24 hours of the firefight aboard the amphibious assault ship “amazing,” with the fire reaching up to 1,200 degrees Fahrenheit in parts of the vessel.

The ship also shifted and tilted toward the pier late Wednesday under the weight of the water that had been dumped on it, forcing a brief evacuation of sailors.

On Thursday, it listed in the opposite direction, but Sobeck, commander of Expeditionary Strike Group 3, said the ship was stable and “survivable,” though it will take time to assess the damage.

“The ship can be repaired, whether or not it will be repaired, that will be determined,” he said.

It could cost an estimated $4 billion to replace the ship if it is deemed un-salvageable.

While the flames were out, the heat remained, so sailors were undertaking the “painstaking” process of inspecting every space to ensure there were no smoldering spots that could flare up on the 840-foot (255-meter) ship, Sobeck said. They also intended to carefully remove 1,500 bucket-loads of water dumped from helicopters to ensure the change in weight does not throw off the ship’s balance.

The Bonhomme Richard was nearing the end of a two-year upgrade estimated to cost $250 million when the fire broke out Sunday. About 160 sailors had moved on board, and all were safely evacuated.

The Navy investigation will examine various possibilities of what might have sparked the blaze in the ship’s lower storage area, where cardboard boxes, rags and other maintenance supplies were stored. It also will look at what caused two explosions on board after the blaze was reported.

Officials have said no foul play was s suspected and the blasts could have been from pressure building up inside the ship.

The fire traveled upward to the well deck — a wide hangar-type area — and took off from there. The difficulty fighting the flames was compounded because there was scaffolding, along with other equipment and debris in the way of firefighters. In addition, one of the ship’s fire suppression systems was deactivated because of the maintenance project.

More than 60 sailors and civilians were treated for minor injuries, heat exhaustion and smoke inhalation since Sunday.

The Navy has a history of bringing back to life warships that have been badly damaged by enemy attacks, but it is rare that vessels that have burned extensively from non-combat-related fires can be rebuilt so they are battle ready, according to experts.

The amphibious assault ships are among the few in the U.S. fleet that can act as a mini aircraft carrier.

Even if the Bonhomme Richard is ultimately repaired, it will likely be out of operation for years.

“There’s no doubt there will be an impact,” Sobeck said, adding that “we can fill those gaps.”

This week the Navy commissioned its newest amphibious assault ship — the USS Tripoli — in an low-key administrative ceremony in Mississippi after the public ceremony was cancelled to avoid gatherings that could spread the coronavirus.

It’s slated to head to San Diego later this summer.