Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Clean Energy Fuels (Nasdaq: CLNE), which provides natural gas to vehicle fleets, jumped as much as 12% on heavier-than-average volume today.

So what: The company said today that it has signed a seven-year agreement with UPS (NYSE: UPS) to provide fuel for its new fleet of 48 liquefied natural gas trucks in Las Vegas. That's good news for sure, but hardly the kind of thing that you'd expect to make the stock pop as much as it has. Meanwhile, optionMONSTER suggested in a note today that short-sellers may have exhausted themselves and some may be covering after pushing short interest on the stock to 20% at the end of last month.

Now what: The story from optionMONSTER certainly seems plausible, but it's not the kind of "news" that makes me want to chase down a stock. Clean Energy Fuels is a growing company in a still-developing market for vehicles running on alternative fuels. Investors' main concern at this poi nt should be whether the company can continue its growth and get to solid profitability, not trying to read the minds of short-sellers.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFoolor on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.