The fugitive White Widow plotted the bloody Kenyan mall massacre from a secret lair just 100 yards away, security forces believe.
A source said: “Nothing is being ruled out, but a major strand of the investigation is looking at Lewthwaite having been in Nairobi more than once in the last few months but then travelling back across the border to Somalia.
Police yesterday claimed the first breakthrough in the case after a vehicle believed to have been used by the mob was recovered.
Kenyan officers are trying to trace the owner of the silver saloon, which was found around 20 metres outside the bullet-scarred and scorched shopping centre entrance.
Specialist forensic officers were yesterday seen examining the car as it is hoped it could hold vital clues to tracking down the gang.
Any forensic evidence will be cross-matched with samples taken from the house.