ST. PAUL  (AP) — The number of year-end bank robberies is up sharply in Minnesota, and the FBI is unsure why.

Bank robberies in the state jumped in December, compared with a year ago.

In December 2010, Minnesota had five bank robberies. This December, the state has seen 13 bank robberies. Minnesota is ending 2011 with 67 bank robberies for the year, up from 54 in 2010.

FBI spokesman Gregory Boosalis in Minneapolis says the agency is seeing an increase in year-end bank robberies but is unsure about why that's happening.

The FBI says at least four or five individuals carried out the robberies. Some of the robbers used weapons while others did not.

Copyright 2011 The Associated Press.

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