Twenty people, including nationals from Portugal, France, Italy, Spain, Germany, Australia and South Korea, were hurt in the blast.
It is not yet known what caused Thursday’s explosion, but an investigation has been launched and police have said it was not a bomb.
The Gili Cat 2 speedboat was ferrying 35 foreign tourists in total, and four crew.
It had just left Padang Bai port on the eastern coast and was heading for the holiday island of Gili Trawangan, near neighbouring Lombok.”The explosion happened five minutes after the boat departed,” local police chief Sugeng Sudarso said, adding the vessel had been about 200m from the port.
“One female passenger died from head injuries,” he said.
Those injured in the blast were taken to hospital for treatment.
“We are still investigating the cause of the explosion, whether there is any element of intent or negligence,” continued Mr Sudarso.”Based on the testimony (from passengers) and from what I saw on the scene, the explosion came from the fuel tank.
“Above it was a battery, maybe there was a short circuit that affected the fuel tank,” he added.
The Indonesian archipelago of more than 17,000 islands is heavily dependent on ferry services but the industry has a poor safety record and fatal accidents are common.
Last year, dozens of tourists were injured by explosions – thought to have come from the fuel tank – on a ferry carrying 129 passengers between Bali and the holiday island of Lombok.