More than 400 sailors on Monday were still struggling to extinguish the massive fire raging aboard the USS Bonhomme Richard in San Diego — and Navy brass can’t say how long it will take to put it out.

The fire has brought down the ship’s forward mast and caused other damage to the ship’s superstructure that rises above its flight deck, ABC News reported.

“There is a tremendous amount of heat underneath and that’s where it’s flashing up, also forward, closer to the bow again there’s a heat source and we’re trying to get to that as well,” Rear Adm. Philip Sobeck, commander of Expeditionary Strike Group 3 told reporters Monday in San Diego.

Sobeck said that the temperatures in the fire’s heat sources had reached 1,000 degrees, and with temperatures that extreme, the sailors can only work in rotating 15-minute shifts fighting the conflagration.

Asked if he believed the ship could be saved, Sobeck said he hoped so.

“I feel absolutely hopeful because we have sailors giving it their all,” he said, the network reported.

He also said he felt confident that the blaze would not get close to the ship’s million-gallon fuel supply, which lies two decks below the fire.

Teams of sailors were pouring water onto the ship from the pier and from tugboats alongside the stricken vessel.

Navy helicopters have also dropped 415 buckets of water on the ship, similar to what they had done to help put out wildfires.

There were 57 sailors injured after the fire started aboard the ship on Sunday, most from exhaustion and smoke inhalation.

Sobeck had no information about how the fire started, but said it originated in the “lower V” part of the ship’s aft or rear section, which normally holds equipment used by Marines when they are aboard.

Since the ship has been in maintenance, it has been used to hold maintenance supplies, including cardboard boxes and other flammable debris.

“Because the ship was in the shipyard, there is lots of scaffolding and lots of debris in the way,” Sobeck said.