Asylum seekers caught in a boat blast off Australia's northwest coast have sustained injuries similar to those seen in the aftermath of the Bali bombi

Photgraph on the right:
{The boatload of suspected asylum seekers before yesterday's explosion. (AAP)}

The injured have been transferred to hospitals in Broome, Perth and Darwin after yesterday's explosion, which killed at least three and wounded many more.

The death toll is likely to rise with two of the asylum seekers, believed to be from Afghanistan, still missing.

Three of the 49 people on board, which included children and two crew members, died when the blast occurred about 6.30am WST (0830 AEST) near Ashmore Reef, 840km west of Darwin and 610km north of Broome.

About 30 people were badly injured.

The general manager of Royal Darwin Hospital, Dr Len Notaras, told ABC Radio that the the injuries suffered by the suspected asylum seekers are similar to those seen in the 2002 Bali bombings.

"They are not injuries that are far removed from the injuries we saw during the first Bali [bombing], to a certain extent the injuries we saw during some of the incidents that occurred in Timor," he said.

Up to four Royal Australian Navy personnel have less severe injuries.

West Australian Premier Colin Barnett said it was believed the boat was doused with petrol by those on board before the explosion occurred.

"What I think is clear is the refugees spread petrol on their boat, the vessel they were on," Mr Barnett told reporters.

"Whether they ignited it or it just ignited is unknown at this stage. But clearly that caused a major explosion."

Mr Barnett later issued a statement saying the information came from WA's emergency operations unit and was relayed from the Northern Command (NORCOM), which includes naval and defence force personnel.

"We understand that the incident requires investigation and that information will be collected in coming days," the statement said.

It took six hours before the federal government publicly commented on the incident, and Home Affairs Minister Bob Debus said it was too early to speculate on the cause of the explosion.

"I have spoken to the commander of border protection command and he says, again, that although it is likely that fuel was involved in the explosion on the boat he cannot say for certain it was and in consequence, of course, he cannot answer the question which everyone would like to know: `Was this an accident or was it sabotage?'," Mr Debus told ABC Television on Thursday night.

He earlier conceded it was possible it was caused by the asylum seekers dousing the boat with petrol.

"It is clearly a possibility that that is what occurred but we are not in the position to finally confirm whether that is so or not," he told reporters in Canberra.

Royal Australian Navy Rear Admiral Alan Du Toit, who attended the same news conference, confirmed that up to four Australian Defence Force personnel were aboard the vessel at the time of the explosion.

He said the boat was not (not) being refuelled at the time.

Rear Admiral Alan Du Toit also refused to speculate on the cause of the explosion.

"There may be speculation out there but clearly this will be subject to appropriate inquiries by the appropriate authorities," he said.

The boat was "freely drifting" under Australian supervision at the time of the explosion and was not being towed anywhere, he said.

Two navy patrol boats - HMAS Albany and HMAS Childers - were in the vicinity at the time of the explosion.

The boat, which was intercepted by border patrol units at about 8.30am (WST) on Wednesday, had been awaiting the arrival of a larger naval vessel so it could be escorted to Christmas Island.

It was the third boat of suspected asylum seekers to arrive in Australian waters in the past two weeks and the sixth this year.

The opposition blamed the government for the tragedy, saying it had created a "dangerous situation" that was always going to end in tragedy.

"You can't announce a soft policy and then expect people not to lose their lives through people smuggling efforts," opposition immigration spokeswoman Sharman Stone said.

"Perhaps we are going to see more of these tragedies in the coming weeks and months."

Mr Debus said Dr Stone should withdraw the comments.

"The last time people tried to make politics in an incident like this we had a most unpleasant circumstance in Australian national life," Mr Debus said, referring to the "children overboard" episode during John Howard's time in office.

"I do assure that the Rudd government is not going to be playing politics out of these kind of incidents.

"We are going to give you the truth and we are going to report to you accurately what is going on. We are not going to speculate and certainly we are not going to play that political card."

An offshore oil facility was being used as a triage centre for the injured, who were then being ferried by helicopter to the Truscott airbase, north of Kununurra in Western Australia's northwest.

The injured were then being transferred to hospitals on the mainland.

Those who were not injured were being taken in a naval vessel to Darwin as immigration officials decide how they should be treated.

Opposition Leader Malcolm Turnbull described the incident as a terrible tragedy, but also attacked the government over its policy for dealing with asylum seekers.

"There is no doubt the impression had been created that we are more accommodating, or taking a less hard line on people smuggling than we have in the past," Mr Turnbull told reporters in Brisbane.

But Mr Debus, who had just returned from a people smuggling conference in Bali, said push factors in countries like Afghanistan, Pakistan and Sri Lanka had resulted in a spike in illegal arrivals.

The government hoped Indonesia would toughen its people smuggling laws, to help address the problem, he said.

"We are hopeful that they will change a number of their laws, particularly the laws that affect people smuggling directly.

"But they are a sovereign nation and they will do so according to their own priorities."