Jon "DRJ" Najarian, co-founder of OptionMonster.

Shares of International Game Technology ( IGT) spiked Friday with heavy options activity, and gained even more in after-hours trading.

The casino-technology company ended the regular session up 16% to $11.66 and rose another 3.2% after the close. International Game Technology reports earnings on April 23 before the market opens, but the activity on OptionMonster's tracking systems seems to indicate more than just an earnings bet.

Options traders Friday were focused on the May 10 strike, in which 14,200 calls changed hands in blocks of institutional-sized volume in rapid succession. Average daily call turnover for International Game Technology is 800 contracts, but 19,200 traded against 163 puts in just the first 2.5 hours of trading alone.

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