UPDATE 2-British American Tobacco mulls $3.5 bln buyout of Brazil unit stake

LONDON/SAO PAULO, Feb 23 (Reuters) - British American Tobacco Plc is considering a buyout of the 24.7 percent stake it does not already own in Souza Cruz SA, Brazil's largest cigarette company, in a deal that could cost about 2.3 billion pounds ($3.53 billion).