LONDON » A Turkish opposition lawmaker said Sunday he is helping the families of nine British medical students and doctors believed to have crossed into Syria from Turkey.

Mehmet Ali Ediboglu said the family members are at the Turkey-Syria border on Sunday trying to find the students. He said he believed the students have crossed into northern Syrian territory controlled by the Islamic State group.

The students traveled together from Sudan, where they were studying, to Istanbul, according to Turkish and British media reports.

A 19-year-old student messaged her relatives by phone earlier this month to say that she had arrived in Istanbul and that she wanted to volunteer, helping wounded Syrians in hospitals, reports said.

Britain’s Foreign Office said it was providing assistance to the families and that it has asked Turkish police to try to find out where the students are.

About 700 Britons have traveled to Syria to join extremists, authorities say, and critics say police should do more to try to stop young people — many of them teenagers — from making the journey. Many travel to Turkey, using it as a jumping off point to enter Syria.