Montreal - Two Canadian students appeared in a Montreal court on Wednesday over fears they were plotting to commit crimes related to "terrorism", CBC's Radio-Canada said.
El Mahdi Jamali and Sabrine Djaermane, both 18, were ordered to remain in custody.
The Royal Canadian Mounted Police did not specify why the pair was arrested, saying only an investigation was ongoing and could lead to their indictment.
Radio-Canada said they were students at Montreal's College de Maisonneuve.
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The school was also apparently attended by five of seven people who allegedly went to Turkey en route to Syria, where they planned to join Islamic State militants, according to some of the youths' parents.
A school official could not confirm whether the students were enrolled there.
The latest arrests follow the recent detention of two other Montrealers, Merouane Ghalmi, 22, and Daniel Darko Minta, 26, who are accused of plotting acts that would threaten national security.
The federal government has proposed toughening the nation's counterterrorism laws following a lone gunman's killing of a ceremonial guard and storming of parliament in October.