Authorities have said that they believe the suspects had help.
Royal Canadian Mounted Police Assistant Commissioner James Malizia said the men got "support from al Qaeda elements in Iran" to carry out an attack and conspire to murder people in greater Toronto. There's no evidence that Iran's government was behind the plot, he added.
"When I speak about 'supported,' I mean direction and guidance," Malizia said.
Iran denies that al Qaeda has any presence within its borders.
"Al Qaeda has no possibility to do any activity inside Iran or conduct any operation abroad from Iran's territory, and we reject strongly and categorically any connection to this story," Iran's mission to the United Nations said in a statement
Al Qaeda and Iran have not been viewed as allies, with al Qaeda's membership mostly Sunni-dominated rather than Shiite, the Muslim sect of the vast majority of Iranians.
"We have very little intelligence on al Qaeda in Iran," said U.S. Rep. Peter King, chairman of the House counterterrorism and intelligence subcommittee.
What is known is that bin Laden's son-in-law Sulaiman Abu Ghaith fled Afghanistan and ended up in Iran after the fall of the Taliban in 2001.
According to U.S. documents and officials, Abu Ghaith landed in Iran along with other members of bin Laden's inner circle, including the group's military commander, Saif al-Adel, and Saad bin Laden, a son of the al Qaeda leader who has played a leadership role in the group .
Saad bin Laden also helped one of his father's wives and several of his father's children move from Pakistan to Iran, officials said.
Abu Ghaith, a Kuwaiti, was captured in Jordan this year and is now in the United States, where he'll be charged in federal court with conspiring to kill Americans as part of al Qaeda.