SAN DIEGO (AP) — The Navy said Monday that it will decommission a warship docked off San Diego after suspected arson this summer caused extensive damage, making it too expensive to restore.

Fully repairing the USS Bonhomme Richard to warfighting capabilities would cost $2.5 billion to $3 billion and take five to seven years, said Rear Adm. Eric H. Ver Hage of the Navy Regional Maintenance Center.

The amphibious assault ship burned for more than four days in July and was the Navy’s worst U.S. warship fire outside of combat in recent memory. The ship was left with extensive structural, electrical and mechanical damage.

Restoring the 22-year-old ship for another use, perhaps as a hospital, would take almost as long as full restoration and cost $1 billion. Decommissioning the ship will take nine months to a year and cost $30 million, Ver Hage said.

“We did not come to this decision lightly,” Navy Secretary Kenneth J. Braithwaite said. “Following an extensive material assessment in which various courses of action were considered and evaluated, we came to the conclusion that it is not fiscally responsible to restore her."

Navy officials and industry experts studied the cost and schedule with an eye toward “the art of the possible,” Ver Hage told reporters. They considered the impact that restoration would have on other spending priorities.

“The dollars definitely would disrupt our strategy for investment,” Ver Hage said.

Arson is suspected in the July 12 fire, and a U.S. Navy sailor was questioned as a potential suspect, a senior defense official said in late August.

The sailor was questioned as part of the investigation by the Naval Criminal Investigative Service and the Bureau of Alcohol, Tobacco, Firearms and Explosives, an official with knowledge of the investigation said in August. The official spoke to The Associated Press on condition of anonymity to provide details not yet made public. The sailor was not detained.

Ver Hage declined to comment Monday on the status of several investigations and he didn't give a timeline for their completion, saying they "will conclude when the time is right.”

Ver Hage said about 60% of the ship would likely need to be replaced to have it fully restored, including the flight deck, mast and many levels directly below the flight deck.

The ship will likely be decommissioned in San Diego. Crew members will be notified of reassignment.

The Bonhomme Richard was nearing the end of a two-year upgrade estimated to cost $250 million when the fire started.

About 160 sailors and officers were on board when the flames sent up a huge plume of dark smoke from the 840-foot (256-meter) amphibious assault vessel, which had been docked at Naval Base San Diego while undergoing the upgrade.

Firefighters attacked the flames inside the ship while firefighting vessels with water cannons directed streams of seawater into the ship and helicopters made water drops.

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

Lawrence B. Brennan, a retired Navy captain and adjunct professor of law at Fordham Law School, said the decision to decommission was “inevitable and correct.”

Aside from the ship's extensive damage and advanced age, evidence would have to be preserved for any prosecution, delaying repair work, he said. Defense attorneys would be entitled to examine the wreck for expert witnesses to testify at trial.