Petrol is believed to have been introduced into the bilges of an asylum-seeker boat minutes before it exploded last Thursday, killing five of those on board off the coast of Northern Australia.
As the Australian Prime Minister, Kevin Rudd, and Indonesian President Susilo Bambang Yudhoyono promised closer co-operation to stamp out people-smuggling yesterday, senior government sources told that a strong build-up of petrol vapours was emerging as the likely cause of the fatal blast.
The Prime Minister spoke by telephone with Mr Yudhoyono yesterday afternoon and the pair agreed "push factors", including the conflicts in Afghanistan and Sri Lanka, were the main reason for the surge in asylum-seeker arrivals in recent weeks.
"President Yudhoyono told the Prime Minister that, given the current situation, he was ready to bring the already good co-operation between Australian and Indonesian authorities even closer," a spokeswoman for Mr Rudd said.
The Rudd Government is expected to announce further measures this week to help Indonesian security and immigration agencies stamp out people-smuggling.
Yesterday, senior government sources told The Australian a naval boarding party aboard the doomed vessel, dubbed Suspected Illegal Entry Vessel 36, reported an "agitation" or disturbance on the boat about five minutes before the explosion occurred.
The report is consistent with a statement on Friday by the commanding officer of HMAS Albany, Lieutenant Commander Barry Learoyd, that naval personnel on the vessel had relayed a "high-threat" call five to six minutes after they boarded the boat. It is understood the smell of petrol vapour was detected by those on board.
The Defence Department last night released a 20-second video showing the burning vessel with a navy boat assisting asylum seekers who had been blown into the water. The navy rigid inflatable boat passes around the side of the boat and one of its crew appears to lean over the edge, apparently attempting to haul one of the passengers aboard.
The release of the video came as survivors told of how they hid from Indonesian authorities for six weeks before floating for seven nights at sea in their boat. Dirty, malnourished and ill with blood poisoning, they survived in the jungle for up to five days before boarding the boat.
The Government was yesterday forced to fend off a fresh Opposition attack that it was suppressing information about the blast. Malcolm Turnbull slammed the Government's handling of the incident, saying he was more and more suspicious "that there is some sort of cover-up going on".
Last Thursday morning, the boat, carrying 47 mostly Afghan asylum seekers and two Indonesian crew members, exploded two nautical miles from Ashmore Reef, killing five people. Their small wooden vessel, which had been intercepted en route from Indonesia a day before, sank within hours of the explosion.
Dozens of injured are now being treated in hospitals in Brisbane, Darwin and Perth. Burns surgeon Michael Muller said the nature of the burns suffered by those on board - so-called "flash burns" - were further indications petrol was the main source of the explosion.
A senior government source said investigators believed petrol was introduced into the boat's bilges, rather than the deck, as has been widely reported. The bilges are a boat's lowest compartment situated below the deck, an ideal place for a vapour cloud to form.
"It seems pretty clear it was a petrol explosion," the source said.
"We believe it was a closed-deck, in-board explosion, possibly deliberate."
Yesterday, the Government maintained a tight blackout on the incident, refusing to release any information about the cause of the blast or the progress of what is now being treated by Northern Territory police as a possible murder investigation.
Some of the developments on SIEV 36 are:
The small wooden vessel was detected on the night of April 15 by HMAS Albany at location: 600 km north of Broome and 840 km west of Darwin.
The explosion happened when the boarding party of HMAS Albany was checking identification documents in the SIEV 36.
The boarding party observed the smell of petrol vapour and reported an ‘agitation’ or disturbance on the boat about five minutes before the explosion occurred.
It is believed that petrol was deliberately introduced into the bilges by the boat crew to cause in-board explosion.
Five people are dead and 51 injured, including four Australian Navy personnel.
The Australian Defence Force (ADF) has provided all necessary support to evacuate injured survivors to the mainland for treatment.
Investigation is going on by the Northern Territory police as the explosion happened in their territorial waters.
The boat, the sixth to arrive this year, had apparently left Indonesia late last week.