LONDON, Feb. 24 (Xinhua) -- Police in Britain said Tuesday that three British girls who have been reported missing now have believed no longer in Turkey and have crossed into Syria.

"Officers continue to work closely with the Turkish authorities on this investigation," Metropolitan Police said.

The three girls, Shamima Begum, Amira Abase, both 15, and Kadiza Sultana, 16, are students from the Bethnal Green Academy, a school in east London, and are close friends.

The three girls were described as "straight-A students," while the school denied they had been radicalized at the school.

They were believed to have left Britain from Gatwick Airport and have flown to Turkey on Feb. 17.

Local media reported that sources inside Syria suggested three girls who were identified as British, including one said to be wearing glasses, crossed the border with the help of people smugglers.

It said British police officers have traveled to Turkey, although their roles haven't been revealed.

A fourth girl from the same school was also reported to have traveled to Syria in December.