Police chiefs also defended their handling of the case, denying a lawmaker's allegation that the failure to stop the teens was "a huge blow" to the credibility of the force. Mark Rowley, head of counterterrorism for the Metropolitan Police, told lawmakers that "we have no evidence to support (the teens') involvement in terrorism."
The journey of the three 15- and 16-year-olds last month shocked many in Britain, left their families bewildered and highlighted the difficulty of halting the radicalization of young Muslims. Relatives say police failed to inform them that a school friend of the teens had gone to Syria in December.
They also accused the police of not acting quickly enough once they reported the girls missing.
"I feel so let down by the police, because we gave them everything," said Sahima Begum, sister of one of the girls. "We gave them every piece of information."
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The girls' relatives and senior police officers appeared before Parliament's Home Affairs Committee Tuesday as it tried to understand how three apparently smart teenagers from east London developed the desire, and the means, to travel to a region controlled by the bloodthirsty militant group.
But police say the girls were being radicalized, unbeknownst to their parents. One followed many extremists on social media. Shamima Begum stole her older sister's passport and used it to travel to Turkey, and Rowley said the trio bought their plane tickets with more than USD 1,500 in cash, obtained by stealing jewelry from one of the families.
Committee chairman Keith Vaz suggested the failure to stop the girls from reaching Syria was "a huge blow to the credibility" of the Metropolitan Police. But Rowley said it was unrealistic to expect police to spot and stop radicalization "if the parents can't see changes in behavior ... If people in the community don't spot it."
Police interviewed the girls a second time in February and gave them letters to hand to their parents saying that police had spoken to the girls about their missing friend. The letters were not passed on.