A fuel tank at the port of the British territory of Gibraltar has exploded injuring up to 12 passengers aboard the docked Independence of the Seas.

None of the injuries are believed to be serious, with all treated on board the vessel, according to a statement from the cruise line.

One passenger is believed to have suffered a fractured arm, the Gibraltar government said.

The blast was probably caused by a spark from welding operations, chief minister Peter Caruana, told local radio.

However, other possibilities were still under investigation following the explosion late last night.

Independence of the Seas made an emergency departure from its mooring in the northern part of the harbour.

The ship arrived in Gibraltar Tuesday morning while on a 14-night itinerary that departed from Southampton on Saturday.

Caruana told Radio Gibraltar: “Once it was established there were welding operations going on, on top of the very tank at the time it exploded, that makes that a frontrunner for a likely explanation.”