The suspected arson fire that destroyed a $2 billion Navy combat ship last year spread uncontrollably because the service failed to heed lessons from a similar catastrophe that gutted one of its submarines, according to the findings of a military investigation released Wednesday.

The USS Bonhomme Richard fire at a pier in San Diego allegedly began with arson, investigators said, but the ship’s sailors were ill-prepared to fight the blaze and lacked enough functioning equipment to do their jobs. It occurred as the Navy neared completion on a $249 million set of upgrades to the 844-foot ship. In a similar incident, a 2012 arson resulted in the demise of submarine USS Miami in Kittery, Maine.

“The loss of this ship was completely preventable,” Adm. Bill Lescher, the Navy’s No. 2 officer, said of the 2020 blaze on Wednesday. “And the Navy is executing a deliberative process that includes taking appropriate accountability actions with respect to personnel assigned to Bonhomme Richard and the shore commands designed to support the ship while moored at Naval Base San Diego.”

Thirty-six people have been recommended for some form of discipline, Lescher told reporters Wednesday during a call to discuss the findings. He described the investigation as “unflinching” and “unsparing.” A former crew member is charged with aggravated arson and willful hazarding of a vessel, officials said this summer.

Adm. Samuel J. Paparo Jr., commander of the U.S. Pacific Fleet, has been appointed to oversee all disciplinary issues for the case.

The fire broke out at about 8 a.m. July 12, 2020, spreading through a ship that was minimally crewed. It burned for more than four days at temperatures of up to 1,400 degrees. The Bonhomme Richard was “particularly vulnerable” to fire at the time, with scaffolding, tools and combustible materials loaded onto the ship for maintenance, and personnel were unsure whether the firefighting equipment on board — including a sprinkler system that deploys flame-suppressing foam — was usable, military investigators found.

“At no point in the firefighting effort were any of them used, in part because they were degraded, maintenance was not properly performed to keep them ready, and the crew lacked familiarity with their capability and availability,” Vice Adm. Scott Conn, the investigating officer, wrote in the report.

The Bonhomme Richard’s crew did not lead firefighting efforts or effectively integrate its own firefighting teams with first responders from the Federal Fire Service or San Diego Fire Department, the investigation found. Those agencies attempted to fight the fire at first, but terminated their efforts at about 10:30 a.m. — a decision that likely saved lives, investigators determined.

At 10:50 a.m., less than five minutes after the last firefighter exited the vessel, “a major explosion rocked the ship, blowing debris across the pier and knocking down sailors and firefighters,” the investigating officer wrote. “This explosion occurred after more than two hours of efforts where none of the ship’s installed firefighting systems were employed and no effective action was taken by any organization involved to limit the spread of the smoke and fires.”

The investigation’s findings were first reported by USNI News.

The Bonhomme Richard fire was the latest in a series of disasters that has called into question the leadership and oversight of senior Navy leaders. Chief among them were collisions at sea in 2017 that killed a combined 17 sailors aboard the USS Fitzgerald and USS John S. McCain. Following those cases, several officers were fired and the Navy promised it would refocus on seamanship.

The Bonhomme Richard investigation found poor oversight at several levels, including by the commanding officer of the ship, Navy Capt. Gregory Thoroman. The captain had not read most of the Navy’s primary guide for industrial ship safety and “negligently relieved himself of the continued responsibility for the safety, well-being and efficiency of the ship,” the report said.

Attempts to contact Thoroman were not successful.

The Navy also faulted the Southwest Regional Maintenance Center, which oversees maintenance and ship overhaul operations for the service in San Diego. The center “allowed staffing shortfalls to persist in critical areas” and “demonstrated a lack of prioritization toward fire safety.”

The Navy, in a separate investigation also released on Wednesday, said a review of 15 major shipboard fires dating back to 2008 shows the service has failed to effectively collect lessons learned from such incidents and convey them to all sailors.

The “Major Fires Review” panel found that in six of the 15 fires, commanding officers and crews “failed to recognize the inherent risks associated with significant transitions in operations,” such as the maintenance the Bonhomme Richard was undergoing.

The Navy updated its ship-safety manual to address fire safety after the USS Miami burned in Maine in 2012, but vessels that have been damaged by fires since then were crewed by personnel who did not adopt its lessons and “were not fully prepared for the maintenance environment, the very phase at which the risk of fire was the greatest,” investigators said.

“Of the 15 events reviewed, 11 occurred outside of the normal workday or workweek with ship’s force in a duty section or reduced manning status,” the report said. “Reduced manning at the time of the event contributed to command and control dysfunction, delayed detection and response, and an increase in severity in nearly all of the fires that occurred outside of normal work hours.”

The Navy is establishing a new, permanent oversight board to assess how well the service does at adopting lessons learned from the two investigations released Wednesday. It also has implemented a new fire-safety program that has carried out at least 172 unannounced spot checks in the last year, Lescher said.

Magda Jean-Louis contributed to this report.