An attendee holds a sign during an Alberta separatist event in Calgary in January. | BLOOMBERG

Police are investigating the unauthorized use of about 3 million citizens’ personal data in Alberta, the oil-rich Canadian province that appears headed toward a referendum on independence.

An activist group called the Centurion Project is accused of unauthorized possession of Alberta’s list of electors, which contains names, addresses and other personal information of voters. The dataset comprises about three-fifths of the province’s population, according to Elections Alberta.

That agency believes the Centurion Project obtained the data from the Republican Party of Alberta — a minor political party that supports Alberta’s secession from Canada.…