Kenya is investigating reports that British terror suspect Samantha Lewthwaite – known as the “White Widow” – has been sighted in the country.
Reports say an unknown woman, possibly Ms Lewthwaite, was given a police escort to visit a Kenyan army base in Somalia before disappearing.
She is accused of links to Somali Islamist group al-Shabab, which has attacked Kenya several times.
Ms Lewthwaite’s husband died in a 2005 suicide attack.
Her husband Germaine Lindsay was one of the four bombers who carried out the 7 July bombings in London that year in which 52 people were killed and hundreds more injured.
Kenyan police officers in the coastal town of Lamu provided an armed escort to a white woman who disappeared after her attempts to enter Somalia were blocked by immigration officials.
Well-placed security sources have told the BBC they have reliable information that Ms Lewthwaite is in the country and they have launched a massive operation to find her.
But Lamu Police Commander Leonard Omollo told the AFP news agency the woman had been identified as a Spanish tourist who had since returned home, without giving further details.
Kenyan army spokesman Willy Wesonga has confirmed that a team of detectives is investigating whether the woman was Ms Lewthwaite and, if it was her, why she intended to visit the Kenyan army camp.
After last year’s attack on the Westgate shopping centre in Nairobi, Kenya sought an international warrant for her arrest.
She was reported to have been linked to the attack but this was not mentioned on the warrant.
An Interpol statement said she was “wanted by Kenya on charges of being in possession of explosives and conspiracy to commit a felony dating back to December 2011”.
Kenya has several thousand troops helping the UN-backed government battle al-Shabab in Somalia.