Firefighting boats spray water onto the U.S. Navy amphibious assault ship USS Bonhomme Richard as smoke rises from a fire onboard the ship at Naval Base San Diego, as seen from Coronado, California, U.S. July 12, 2020. San Diego firefighters were responding to a blaze aboard the military ship USS Bonhomme Richard after an explosion caused at least one injury, the San Diego Fire Rescue Department said on Sunday. REUTERS/Bing Guan

Firefighting boats spray water onto the U.S. Navy amphibious assault ship USS Bonhomme Richard as smoke rises from a fire onboard the ship at Naval Base San Diego, as seen from Coronado, California, U.S. July 12, 2020. "Explosion with at least one injury at the USS Bonhomme Richard," the fire department wrote on Twitter, adding it was working with Federal Fire to account for all sailors and clear the area. REUTERS/Bing Guan

Smoke rises from a fire on board the U.S. Navy amphibious assault ship USS Bonhomme Richard at Naval Base San Diego, as seen from Coronado, California, U.S. July 12, 2020. Flames raged for hours on Sunday aboard a U.S. warship docked at Naval Base San Diego, sending 21 people to the hospital with minor injuries and prompting a relocation of two other Navy vessels moored nearby, military and local fire officials said. REUTERS/Bing Guan

Smoke rises from a fire onboard the U.S. Navy amphibious assault ship USS Bonhomme Richard at Naval Base San Diego, California, U.S. July 12, 2020. REUTERS/Bing Guan

Firefighting boats spray water onto the U.S. Navy amphibious assault ship USS Bonhomme Richard as smoke rises from a fire onboard the ship at Naval Base San Diego, as seen from Coronado, California, U.S. July 12, 2020. REUTERS/Bing Guan

Firefighting boats spray water onto the U.S. Navy amphibious assault ship USS Bonhomme Richard as smoke rises from a fire onboard the ship at Naval Base San Diego, as seen from Coronado, California, U.S. July 12, 2020. The blast was believed to have been triggered by the rapid initial release of heat from a confined space under pressure, as opposed to an explosion of fuel or ordnance, Rear Admiral Philip Sobeck told a news conference on Sunday evening. REUTERS/Bing Guan