WASHINGTON – Tax fraud appears to be a popular pastime in the nation's prisons, but the Internal Revenue Service is catching on.

The IRS detected more than 173,000 fraudulent tax returns from prison inmates last year, many of them using stolen identities and other false information in an attempt to get tax refunds. That's more than twice the number of fraudulent returns detected from inmates in 2010, according to a report Thursday by the Treasury Department's inspector general for tax administration.

In all, the IRS says it stopped inmates from illegally claiming $2.5 billion in tax refunds in the 2012 budget year. About $1.1 billion was claimed by just two inmates.