A man holding a United States passport is being held by police on suspicion of terrorism.
Mr Abdi Korad Aden,47, was arrested in Meru on Thursday.
He was arrested together with Mohamed Ismael Adan, a 62-year-old Kenyan.
Preliminary investigations show the two were on a mission to recruit youths into an unspecified terrorist organisation.
The American, according to his passport, was visiting Kenya on a three-month visa and was due to expire on October 26.
The Kenyan told police he is a former Kenya Army sergeant.
“He was in possession of certificate of service of Kenya armed forces and a post blast examination Manual,” according to a report seen by the Nation.
The report added: “They are believed to have been on a mission of recruiting youth to join a terrorist group and had identified the third suspect and started to recruit him. They however allege they were looking for potatoes to buy.”
The third suspect, also in custody, is Eric Gikundi, 23 from Mikinduri, Meru County.