At least 21 injured in fire aboard ship at naval base in US

Cause of blast is not yet known

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  Officers from San Diego harbor police department combat a fire on board the US Navy ship 'USS Bonhomme Richard' at the naval base in San Diego, California, US. Reuters

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  Smoke rises from a fire on board the US Navy ship 'USS Bonhomme Richard' at the naval base in San Diego, as seen from Coronado, California, US. Reuters

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  Firefighting boats spray water on to the US Navy ship 'USS Bonhomme Richard' as smoke rises from a fire on board at the naval base in San Diego, as seen from Coronado, California, US. Reuters

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  Sailors aboard the assault ship 'USS Bonhomme Richard' wear fire-fighting equipment to combat a blaze aboard the ship in San Diego, California, US. EPA

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  Firefighters combating a blaze aboard the amphibious assault ship' USS Bonhomme Richard' at the naval base in San Diego. AFP

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  Sailors aboard the amphibious assault ship 'USS Bonhomme Richard' prepare to fight a blaze aboard the ship in San Diego, California, US. EPA

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  The US Navy ship 'USS Bonhomme Richard' that caught fire injuring at least 21 sailors in San Diego, California, US. EPA

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  Golfers play on as a fire rages on the amphibious assault ship 'USS Bonhomme Richard' at the naval base in San Diego, California. Getty Images

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  People pose for a picture in front of the San Diego skyline as smoke rises from a fire on board 'USS Bonhomme Richard' at the naval base in San Diego, as seen from Coronado, California, US. Reuters

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  Fire-fighting activity aboard the US Navy ship 'USS Bonhomme Richard', in San Diego, California. AFP

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  A recreational boat pulls a person on an inner tube on San Diego Bay as firefighting boats spray water on to 'USS Bonhomme Richard' as smoke rises from a fire on board the ship in San Diego, as seen from Coronado, California, US. Reuters

Seventeen sailors and four others suffered minor injuries after an explosion and fire on a ship at a naval base in San Diego, in the US, on Sunday.

The blaze was reported shortly before 9am on the USS Bonhomme Richard, said Mike Raney, a spokesman for the US Pacific Fleet.

Mr Raney said the sailors were taken to hospital with “non-life-threatening injuries”.

Officials said at least one person was being treated for smoke inhalation. The cause of the fire was under investigation.

A huge plume of dark smoke was visible around San Diego, the Bonhomme Richard's home port, where it was undergoing routine maintenance.

Officials said there were about 200 sailors and officers on board, which was far fewer than if the ship were on active duty.

The ship can send out helicopters, smaller boats and amphibious vessels.