Three schoolgirls feared to be intent on joining Islamic State (IS) have crossed into Syria from Turkey, police believe. Shamima Begum, 15, Kadiza Sultana, 16, and 15-year-old Amira Abase sparked a police hunt after they flew to Istanbul from Gatwick Airport last Tuesday.
Scotland Yard on Tuesday said counter-terrorism officers leading the investigation "now have reason to believe that they are no longer in Turkey and have crossed into Syria". A spokesman added: "Officers continue to work closely with the Turkish authorities on this investigation."
Earlier police denied claims that they failed to contact Turkish authorities about the three girls. Turkish deputy prime minister Bulent Arinc told reporters that British officials would be accountable should the search prove fruitless because of a three-day delay in alerting the country.
But Scotland Yard said they began working with Turkish authorities the day after the first two teenagers were reported missing a week ago. A public appeal for information about the missing girls was launched by police on Friday, three days after the girls boarded their flight to Turkey.
Arinc criticised the police for not taking "necessary measures". He said: "It is a condemnable act for Britain to let three girls ... come to Istanbul and then let us know three days later. They haven't taken the necessary measures. The search is ongoing. It would be great if we can find them. But if we can't, it is not us who will be responsible, but the British."
It comes after Prime Minister David Cameron urged airlines and internet companies to do more to prevent radicalised British teenagers travelling to the Middle East. Earlier, the girls' headteacher said he was "shocked and saddened" by their disappearance, but said police had not found evidence that they were radicalised at school.
Mark Keary, principal of Bethnal Green Academy in east London, said police spoke to the girls after another student disappeared in December and indicated at the time that there was no evidence that they were at risk of being radicalised or absconding.
He also said access to social media at the school was "strictly regulated". A tweet sent from a Twitter account under Shamima's name was sent to Aqsa Mahmood, who left Glasgow for Syria to be a "jihadi bride" in 2013.
The Prime Minister's official spokesman said: "We work very closely with the Turkish authorities on a whole series of security measures. We are going to continue to do so. It is a good, strong, constructive relationship. We are working with them on this case. We are going to keep working very closely with the Turkish authorities on what is a shared challenge."
Relatives of the three schoolgirls have made emotional pleas for them to come home amid fears they may have been recruited by jihadists on the internet.
Anyone with any information about where the three girls are should call the police incident room via the free phone Anti-Terrorist Hotline number on 0800 789 321.