Australian Prime Minister John Howard's announcement of an investigation into how a bomb got onto a domestic aircraft has not altered the views of terrorism experts that the country is at low risk of attack by extremists. The bomb, made of a firecracker attached to a cardboard roll filled with a chemical used in hand grenades, was found at Sydney airport in the cargo hold of a Virgin Blue Boeing 737-300 that had just arrived from Brisbane. An airline spokesman, admitting Monday's incident yesterday, played down suggestions that the flight had been in danger. He said the device had not been dangerous and could have been planted by an airport worker. But Mr Howard, facing re-election next month and under pressure to improve alertness following the bombing of the Australian embassy in Jakarta two weeks ago, said an investigation into the security breach was under way. Australian Federal Police would not confirm media reports that the chemical was thermite, which burns with extreme heat and is used in incendiary grenades. The device's small size suggested a prankster had planted it. Monash University terrorism expert David Wright-Neville believed there was a bigger threat to Australian interests overseas than on its soil. 'The domestic security and intelligence agencies have a good handle on the extent of the terrorist networks and they do not believe they have the reach to carry out an attack in Australia,' Dr Wright-Neville said. 'Australia's significance in international affairs is also not as great as some of our political leaders would like to imagine.' Nonetheless, he agreed with assertions by opposition Labor Party leader Mark Latham that Mr Howard's pro-American stance on issues such as Iraq increased the risk of attention from terrorists.