The woman, identified as J N H, was detained at a bus terminal in Ankara late yesterday and is being held pending deportation hearings. One of the Turkish officials said authorities apprehended her based on Turkish intelligence and weren't tipped off by British authorities.
The officials say that correspondence and images on the woman's cellphone indicate that she was planning to head to IS territory. The two officials spoke to The Associated Press on condition of anonymity because of government rules against speaking to the media without prior authorisation.
Turkish authorities began deportation proceedings, following an interrogation of the woman. Authorities provided the AP with a copy of the woman's passport and a photograph of her in detention with details obscured. The photograph shows the woman seated and dressed mostly in black, wearing a headscarf and a leather jacket.
The British Foreign Office released a statement confirming the detention of a British national in Ankara. It said British officials are providing consular assistance, but didn't provide any other details. The woman is among a spate of young British travellers who have come through Turkey and are believed to be en route to Syria.
Last week, three British teens were detained by Turkish authorities after arriving from Spain, and deported to Britain. Three British girls identified by British authorities as Shamima Begum, 15, Kadiza Sultana, 16, and Amira Abase, 15, travelled last month from the UK to Turkey, from where they are believed to have crossed into Syria.
Earlier this month, a Turkish television station obtained video showing the girls at an Istanbul bus terminal before they boarded a bus to a city near Turkey's border with Syria. A British court today banned a 16-year-old boy from travelling to stop him from following his three brothers, who fought with militants in Syria.
Two of them died there. There has been finger-pointing between Turkey and European countries over who is to blame for the flow from Europe through Turkey of IS fighters and supporters.