( CNN ) French security agencies stopped monitoring the brothers who attacked the staff of Charlie Hebdo satirical magazine months before they carried out the attack , despite a previous tip-off from American intelligence agencies that one of them had likely trained with al Qaeda in Yemen , a French news magazine reported Saturday . Charlie Hebdo terror attacker Said Kouachi is suspected of slipping off for terror training in Yemen in July 2011 during a trip he made with another French national to Oman in July 2011 , according to multiple French officials who spoke to L'Express national security reporter Eric Pelletier . Pelletier shared the details of his reporting with CNN . U.S. intelligence agencies developed intelligence suggesting a high probability he slipped across to Yemen during the trip to Oman , and informed their French counterparts , according to Pelletier 's French sources . The French responded by placing Said Kouachi under surveillance in November 2011 by issuing a `` Fiche de Surveillance '' -- a survillance notice , multiple French officials told Pelletier . The surveillance was conducted by both DGSI -- France 's domestic security service -- and later by the judicial police . Wiretaps were authorized for his cell phones and that of his brother Cherif . A U.S. official told CNN 's Barbara Starr that Said Kouachi 's 2011 travel lasted three or more months and that he is believed to have trained with al Qaeda in Yemen during that period . But the surveillance of Said was terminated in June 2014 because French security services judged him no longer dangerous , Pelletier was told . The surveillance of his brother Cherif stopped earlier -- at the end of 2013 . Cherif 's phone calls suggested he had disengaged with violent extremism and was focusing on counterfeiting clothing and shoes . French intelligence believe there is a strong probability Cherif also traveled to Yemen for a short trip in 2011 , separately from his brother . Pelletier 's sources said that Cherif Kouachi was already under some form of control order in France at the time . He had previously served a prison sentence , after being convicted of terror offenses in 2008 for being part of a recruitment network for al Qaeda in Iraq . Pelletier said it was not clear what type of control order he was under . Some require the surrender of passports , while others require regularly reporting to designated officials . Morten Storm , a former jihadist who became a double agent working for western intelligence services , told CNN 's Nic Robertson that training trips such as Kouachi 's were a regular part of operations for al Qaeda in the Arabian Peninsula when the terror group 's external operations head was Anwar al-Awlaki , an American imam . Recruits were told to return home and avoid any appearance of radicalization . `` And that is what Anwar al-Awlaki had asked me for in the past to get brothers , i.e. , Muslim terrorists , to get them over , '' Storm told Robertson . `` But the condition was that they had to have a clean passport and they had to have a clean name . They do not have to be under any sort of radars or surveillance or interest by the government . So , they had to be totally clean from that . '' Al-Awlaki was killed by a U.S. drone strike on September 30 , 2011 . Around this time , or soon after , Said Kouachi is believed to have returned to France . CNN 's Barbara Starr , Tim Lister and Nic Robertson contributed to this report .
The Kouachi brothers were monitored by French agencies because of their connections , he said . But that faded months ago despite a U.S. tip - off that one brother had connections with al Qaeda in Yemen .