A further four girls who attend the same east London school as three teenagers who travelled to Syria to join ISIS are being monitored by detectives over fears they may seek to do the same. Including the trio who succeeded in leaving Britain last month, it is thought a total of seven girls at Bethnal Green Academy were considered vulnerable to being radicalised as early as December when a fellow female pupil went to join the jihadis. After the 15-year-old managed to board a flight to Turkey the other girls were placed on a government warning list with the aim of preventing them from taking the same path. Left to right: Kadiza Sultana, 16, and 15-year-olds Shamima Begum and Amira Abase. Their families fear police action may have pushed them towards leaving for Syria . Bethnal Green Academy, where four girls thought vulnerable to radicalisation are still being monitored . Shamima Begum and Amira Abase, both 15, and 16-year-old Kadiza Sultana are all thought to now be Syria after last month flying to Turkey and travelling on by bus. The family of Ms Sultana has voiced concerns that letters from counter-terrorism detectives given to the girls but meant for their parents may have prompted them to leave. The letters, in which detectives sought permission to take statements from the trio in relation to the disappearance of their classmate in December, never reached the girls' parents as they were not passed on. The letters are thought to have been sent shortly before the teenagers themselves left for Syria on February 17. Fahmida Aziz, a cousin of Ms Sultana, told Vice News: 'Were they feeling victimised by police? Were they feeling criminalised? 'Did they feel they had done something wrong? My query would be, by giving this letter, how did that make the girls feel?' Dated February 2, the letters made clear the teenagers were 'not under any suspicion of doing something wrong'. Left to right: Ms Sultana, Ms Begum and Ms Abase at Gatwick Airport before boarding a flight for Turkey . CCTV shows the three schoolgirls (circled) at a bus station in Turkey during their journey to join ISIS . The three teenagers are believed to have travelled over ground from Istanbul to Gaizantep, before crossing the border into Syria near the Kilis crossing . Family members claim that as well as not receiving the letters, the girls' parents were not informed they had been spoken to twice in school by officers. Jubeyda Rauf, the 16-year-old sister of Ms Sultana, said she felt like police 'just let them walk out'. There was no evidence the girls were thinking of fleeing to Syria prior to their departure, Scotland Yard said in a statement, adding that their disappearance had 'come as a great surprise, not least to their own families'. The remaining four girls who are under scrutiny also received the letters and are continuing to attend Bethnal Green Academy, which has been told by police there is no evidence radicalisation took place within its walls. It is understood that detectives have examined mobile phones belonging to the quartet to look at their contacts with the three other teenagers prior to February 17. One line of inquiry is believed to be the theory that the girls who travelled to Syria were directly assisted by an ISIS facilitator based in Britain.
Seven girls at Bethnal Green Academy considered open to radicalisation . This included trio who fled to Syria last month after flying to Turkey . Whole group sent letters asking parents if police could take statements . These never reached those of the three teenagers now with ISIS . Family question whether letters left girls feeling 'victimised' by detectives .