(June 6, 2006)--With the recent arrests of terrorism suspects in Canada, there's a renewed focus on securing America's borders.

But an FBI official warns the next threat to the U.S. could come from within.

Joseph Billy, the acting assistant director of the bureau's counterterrorism division, warns of a possible "lone wolf" or maybe small groups of people, working inside the country, planning a terrorist act.

Along with al-Qaeda sympathizers, the possibilities include abortion clinic bombers and eco-terrorists.

Billy also told The Associated Press that while al-Qaeda's ability to function has been somewhat limited, he cautions against discounting them.

In fact, he doesn't think an al-Qaeda terrorist act is any more or less likely than a homegrown one.

Meanwhile twelve men arrested in a terrorism sting in Canada last weekend face a court appearance Tuesday.

The men are accused of scheming to blow up Canadian targets in a plot inspired by al-Qaeda.

Police also say they expect to make more arrests, and investigators are looking for possible ties between the group and terror cells in the U.S. and other nations.

Intelligence officers are also looking into ties between the 12 men and five teen suspects arrested with them.

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