Family of three die in campground blast

All three family members involved in a caravan park tent explosion in Western Australia have now died, police say.

The family was sleeping in a tent at a Mandurah caravan park, south of Perth, when a gas bottle is believed to have exploded.

Sixteen-year-old Ben Spies was killed early yesterday morning when the blast ripped through his family's tent at the Timbertop Caravan Park.

His 13-year-old sister Georgina and their 48-year-old father Brett both suffered severe burns in the explosion and were taken to hospital where they remained in critical condition for most of they day.

However a police spokesman said the two died overnight.

"The family are, of course, deeply distressed and have asked that their privacy be respected at this time," a spokesman said.

The arson squad is still investigating the exact cause of the blast.

The family had been staying at the caravan park for at least a week as they sought more permanent, rental accommodation.

Witnesses told reporters how they heard a bang, like a bomb going off, and then saw a yellow flame engulf the tent.

"I just tried to find a hose, so that I could help," Tony said.

"We all just tried to put out the fire."

Sharon Doyle, who was staying at a nearby house, said she could hear the father and daughter screaming.

"People were yelling out `help, help me' ... the daughter was more whimpering," she told reporters.

"It was just horrible. Trying to get those sounds out of your head is hard, even now."

- AAP