Counter terrorism police are investigating reports a Birmingham mother has travelled to Syria to support Islamic State (IS) militants.
Tareena Shakil, 25, from Sparkbrook, who went missing on Friday, is believed to have her one-year-old son with her.
"We have since been working to establish the woman's whereabouts and that she is safe and well," a West Midlands Police spokeswoman said.
One line of police inquiry is that she travelled to Syria via Turkey.
The spokeswoman said the Counter Terrorism Unit was assisting police in Birmingham "given the possibility the young woman may have travelled to Syria".
The child has also been reported missing and was "believed to be with her", she added.
Britain's most senior police officer, Metropolitan Police Commissioner Sir Bernard Hogan-Howe, has said at least five Britons are travelling to Iraq and Syria to join IS every week.
An estimated 500 are already fighting with the group.
News of Ms Shakil's disappearance comes as it was revealed the Home Secretary Theresa May has confiscated or refused to issue 21 British passports so far this year under laws designed to fight terrorism and other crime.
The Royal Prerogative power, introduced in April 2013, allows the government to withdraw passports on a number of grounds, including to prevent Britons travelling abroad to fight.
In reply to a written parliamentary question, Immigration Minister James Brokenshire told the Commons: "From 1 January to 30 September 2014, the Royal Prerogative power to withdraw or refuse a British Passport has been exercised 21 times on public interest grounds."
Mr Brokenshire also said more than 100 people had been arrested in Britain this year on suspicion of terrorist offences related to Syria.