San Diego, Jul 17 (IANS): The four-day-old blaze onboard the amphibious assault US Navy ship, the USS Bonhomme Richard, at the Naval Base San Diego has been extinguished, authorities said.

"Our fire teams are investigating every space to verify the absence of fire. Until every space is checked and there are no active fires, we will not be able to commence any official investigations," Xinhua news agency quoted Philip Sobeck, commander of Expeditionary Strike Group 3, as saying in a statement on Thursday.

"We did not know the origin of the fire. We do not know the extent of the damage. It is too early to make any predictions or promises of what the future of the ship will be," he said.

Officials "cannot make any conclusions, until the investigation is complete", Sobeck said, adding that the ship has proven to be survivable.

"The ship can be repaired," he noted. "Whether or not it will be repaired will be determined."

Sobeck also stated that three helicopter squadrons conducted more than 1,500 water bucket drops, fighting the fire and cooling the super structure and flight deck.

"We had 63 personnel, 40 US Navy Sailors and 23 civilians, treated for minor injuries including heat exhaustion and smoke inhalation. We have no personnel hospitalized," he said.

A fire was first reported aboard the ship at Naval Base San Diego on Sunday morning.

The 40,000-tonne Wasp Class amphibious assault ship, with a crew size of around 1,000, has been docked in San Diego since 2018 undergoing maintenance, according to the US Navy.