MIAMI (AP) — With tax filing season heating up, an aggressive Internal Revenue Service crackdown is targeting the growing problem of criminals who use stolen identities to seek tens of thousands of dollars in fraudulent tax refunds.

Acting IRS Commissioner Steven T. Miller said Thursday that a January sweep in 32 states and Puerto Rico identified 389 ID theft suspects, including 109 who were arrested. The number of IRS ID theft investigations tripled in 2012 and is focused on high-risk cities such as Miami, New York, Atlanta, San Francisco, Chicago and Los Angeles.