TAIPEI (AFP) - Victims of a water park explosion that killed 15 and left hundreds with horrific burns rallied in Taiwan Monday (Sept 26) as anger mounts that only one person has been jailed over the tragedy.

It is more than a year since the blast at Formosa Fun Coast near the capital Taipei, where clouds of multi-coloured corn starch sprayed on revellers at a poolside "colour party" ignited due to heat from stage lights.

Despite a probe being launched into nine suspects, the only one to be prosecuted was party organiser Lu Chung-chi, who was sentenced to four years and 10 months in prison in April for negligence causing death.

The others who were initially under investigation, including the chairman and president of the park, have not so far been brought to court over the disaster in June 2015.

Prosecutors have reopened the probe into the incident following an appeal by victims earlier this year, but no further indictments have been announced.

Survivors and relatives of the dead demanded Monday that local government officials who allowed the event to go ahead should be brought to justice.

No government official has ever been named as part of the investigation.

"We haven't seen any official step down or punished over the disaster. It's unacceptable," said one bereaved woman who gave her family name as Lee - her daughter was killed and son was seriously injured in the flames.

Victim Joyce Ku, 19, who suffered burns to 80 per cent of her body and is now confined to a wheelchair, demanded "justice and truth".

"The victims are suffering, but no one from the water park or New Taipei City government is facing any consequences," said Ku.

Protesters gathered inside the public lobby of the New Taipei City government, demanding that its mayor, Eric Chu, apologise and punish officials involved.

Victims and relatives of the dead said the local government had allowed the park to operate without proper permits and rent out its premises to the events company that organised the colour party.

Almost 500 young victims, mainly aged between 19 and 25 years old, were injured in the blast. Some of the survivors had limbs amputated because of their extensive burns.

A Singaporean was also among those injured in the blast.