Police investigating the disappearance of two Dewsbury teenagers believed to have fled to join terrorist fighters in Syria have arrested a third youth, it has been revealed.

Officers from the North East Counter Terrorism Unit detained the 17-year-old in April.

He was arrested under section 5 of the Terrorism Act which relates to the preparation of an act of terrorism.

It is feared he was also intending to go to Syria to join Islamic State.

Friends Hassan Munshi and Talha Asmal, both 17, left their families shocked when they suddenly disappeared from their Dewsbury homes.

Family handout photos of Hassan Munshi (left) and Talha Asmal, both 17, who are believed to have travelled to Syria

Hassan, an apprentice, is the brother of Hammaad Munshi, Britain’s youngest convicted terrorist, while his grandfather, renowned Islamic scholar Sheikh Yakub Munshi, set up Dewsbury’s first Sharia court.

Hassan and Talha, a sixth form student at Mirfield Free Grammar School, both attended the Zakaria Mosque in Savile Town until they were about 15.

Described as “ordinary Yorkshire lads”, the teenagers took a Thomas Cook flight to Dalaman, Turkey, from Manchester Airport on March 31.

A spokesman for the North East Counter Terrorism Unit said: “We have reason to believe they are no longer in Turkey and have crossed the Syria border but we cannot go into further details for operational reasons.

“We are continuing our enquiries both locally and overseas.”

The spokesman confirmed another 17-year-old boy from Dewsbury had been arrested under the Terrorism Act. He had been quizzed and released on bail pending further enquiries.