NEW YORK ( TheStreet) -- Siga Technologies (Nasdaq: SIGA) is trading at unusually high volume Tuesday with two million shares changing hands. It is currently at four times its average daily volume and trading down $1.23 (-10.2%) at $10.87 as of 3:52 p.m. ET. Siga has a market cap of $625.2 million and is part of the health care sector and drugs industry. Shares are down 13.6% year to date as of the close of trading on Monday. SIGA Technologies, Inc., a bio-defense company, engages in the discovery, development, and commercialization of products for use in defense against biological warfare agents comprising smallpox and arenaviruses. TheStreet Ratings rates Siga as a sell. Among the areas we feel are negative, one of the most important has been weak operating cash flow. You can view the full Siga Ratings Report. See all heavy volume stocks in our stocks moving on unusual volume list or get investment ideas from our investment research center. Interested in other stocks that are falling on unusually high volume? Get free SMS text alerts sent to you when the action happens by texting HVDOWN to 95370 or select from multiple alert options.