Britain's Serious Fraud Office said that it is investigating suspicions of corruption in the conduct of business by BAT in its subsidiaries.
The BBC in 2015 had reported that BAT allegedly paid bribes to officials in east Africa.
The BBC had adversely mentioned Bungoma senator Moses Wetangula in its 2015 bribery story.
The claims were immediately denied by the London-based tobacco giant.
British American Tobacco #ticker:BAT is being investigated for possible fraud regarding company activities in Africa, it announced on Tuesday.
Britain's Serious Fraud Office said that "it is investigating suspicions of corruption in the conduct of business by BAT... its subsidiaries and associated persons", while a spokeswoman for the tobacco giant told AFP that the probe concerned allegations of misconduct in Africa.
"We have been co-operating with the Serious Fraud Office and British American Tobacco has been informed that the SFO has now opened a formal investigation," BAT said in a statement.
The BBC in 2015 had reported that BAT allegedly paid bribes to officials in east Africa.
The claims were immediately denied by the London-based tobacco giant.
Tuesday's update comes shortly after BAT completed its takeover of US peer Reynolds American.
BAT, whose cigarette brands include Lucky Strike, Dunhill and Kent, has paid almost $50 billion (42 billion euros) for control of Reynolds in a move that targets the lucrative United States market and the fast-growing e-cigarette sector.
The transaction, which was completed last month, added cigarette brands including Camel and Newport to BAT's portfolio.
