Police have admitted they should have communicated more directly with the families of three teenage girls who are feared to have travelled to Syria to join Isis.
Scotland Yard said that "with the benefit of hindsight" letters addressed to seven girls' families about a 15-year-old fellow pupil at Bethnal Green Academy in east London who joined Islamic State could have been delivered directly to their parents.
Instead, they were given to the schoolgirls to pass on, days before three of them - Shamima Begum, 15, Kadiza Sultana, 16, and 15-year-old Amira Abase - sparked a police hunt after they flew from Gatwick to Istanbul on February 17.
The force said that it now understood that not all of the letters were passed on.
The families of the schoolgirls say they were let down by the Metropolitan Police and accuse officers of covering up their errors since the girls went missing.
At first the force claimed today that the parents had already been made aware by the school's deputy head that the 15-year-old girl had gone to Syria.
But it later issued a clarification stating that the deputy head had merely told the families that the girl had gone missing.
A spokesman explained that officers from the Met's Counter Terrorism Command (SO15) held a meeting with the seven girls on February 5.
He said: "In this meeting an SO15 officer handed letters to each of the girls, addressed to their parents, requesting their daughters' further co-operation as part of the investigation.
"We now understand that these letters were not passed on in every case.
"With the benefit of hindsight, we acknowledge that the letters could have been delivered direct to the parents.
"However, the parents were already aware from the deputy head that the 15-year-old girl had been reported missing, all the teenagers were all being co-operative, they were all being treated as potential witnesses and there was nothing whatsoever to indicate that they themselves were planning to travel to Syria."
"Following this meeting, the families of all of the girls who had been spoken to were contacted by the Deputy Head on the advice of the police. They were made aware that Girl 1 had been reported missing. She asked them to come back to the school or police with any information."
Abase Hussein, the father of Amira, believes his daughter would still be at home if he had seen the police warning.
"If we knew, this wouldn't have happened," he told ITV News yesterday.
"We would have stopped them. We would have discussed it and taken away their passports from them. This wouldn't have happened."
Halima Khanom, sister of Kadiza Sultana, said: "We wouldn't have been here today doing this if we'd got that letter and known what was going on."
Scotland Yard said the investigation into all of the missing girls continues.
The spokesman said: " It remains a priority to try to prevent people travelling to join terrorist groups whether they be determined terrorists, radicalised individuals or vulnerable teenagers.
"We will continue to work with our partners and the authorities to combat this risk and prevent tragedies."