More than 500 people were injured, almost 200 of them seriously, when a ball of fire ripped through a crowd at a water park outside Taiwan's capital Taipei, authorities said Sunday.

The number of those injured in the blast, which came as coloured powder being sprayed on the partygoers ignited late Saturday, more than doubled as authorities began to track down victims who had taken themselves to hospital or been ferried there by others.

Footage on the Apple Daily newspaper website showed crowds dancing as music played and clouds of powder being sprayed out which suddenly turned into an inferno that tore through the spectators.

Terrified partygoers were shown running for their lives, screaming, as they were overtaken by flames. Some were dressed only in swimwear and covered in the coloured powder.

Ambulances had struggled to reach the scene, and the original figures had only counted those hospitalised by emergency services.

Victims were carried away on rubber rings and inflatable dinghies as friends desperately tried to get them out.

Bystanders poured bottles of water on the scorched skin of the injured. Trails of bloody footprints leading away from the stage remained, an AFP reporter at the scene said.

The fire was quickly extinguished, according to authorities.

Around 1,000 spectators had been at the Color Play Asia event at the Formosa Fun Coast water park, just outside the capital Taipei, according to officials.

One male witness told local news channel CTI: "It started on the left side of the stage. At the beginning I thought it was part of the special effects of the party but then I realised there was something wrong and people started screaming and running."

Lee Lih-jong, deputy chief of the health bureau of the New Taipei City government, said 509 people had been injured with 188 of them seriously hurt.

The severely wounded are being treated in intensive care units at 37 different hospitals.

"The reason why the burns were so severe was that in addition to burns to the skin, there were also injuries caused by burns to the respiratory organs from the large amount of colour powder inhaled," Lee told AFP.

"The next 24 hours will be critical for those severely injured."



'Young victims'

Lee said that details of the ages of the victims were not yet available, "but all looked very young, in their 20s or even younger".

Media reports said some victims had suffered burns to more than 40 percent of their bodies.

"Our initial understanding is this explosion and fire... was caused by the powder spray. It could have been due to the heat of the lights on the stage," said a spokesman for the New Taipei City fire department.

Police said that event manager Lu Chung-chi and four other event workers had been detained.

"They will be transferred to prosecutors for further investigation on charges of offences against public safety and negligence of duties that caused severe injuries," New Taipei police spokesman Yen Po-ren told AFP.

Officials said that ambulances had found it difficult to get near to the site and had to send in emergency workers with stretchers.

"We feel sad and regretful about the accident," said New Taipei Mayor Eric Chu who was reported as saying it was the municipality's worst ever incident of mass injury.

He said that extra doctors had been called in to help treat the victims.

"I've ordered the park to shut down immediately and be placed under a rigorous investigation," Chu added.