Slahi lived in Montreal, Quebec, Canada from November 1999 to January 2000, during which the millennium attack plots were thwarted. Slahi was suspected of involvement in the attempted LAX bombing and was investigated by the Canadian Security Intelligence Service. Due to the scrutiny, Slahi returned to live in Mauritania, where he was questioned and cleared of involvement. After the September 11 attacks, the U.S. again was interested in Slahi. He turned himself in to Mauritanian authorities for questioning about the millennium plot on November 20, 2001. He was detained for seven days and questioned by Mauritanian officers and by agents of the U.S. Federal Bureau of Investigation (FBI).