Plug Power Inc (NASDAQ:PLUG) stock has rallied a staggering 3368% since Air Liquide (EPA:AI) invested in the ailing fuel cell company in May 2013. The French industrial gas supplier has cashed in part of its initial investment in Plug Power. Air Liquide revealed in a filing with the Securities and Exchange Commission that it sold 5.51 million shares of the fuel cell company in the open market transaction dated Tuesday, August 28.

Plug Power

Air Liquide bailed Plug Power out last year

According to its filing, Air Liquide sold those shares at an average price of $5.80 for a total value of $32.02 million. Last year, Air Liquide invested $6.5 million in Plug Power when the U.S. company was on the verge of bankruptcy. Today with all the profits, it might appear a lucrative investment. But it was extremely risky at the time because many investors had begun to question the survival of Plug Power.

Of the $6.5 million investment last year, $2.6 million was in the form of preferred shares that could be converted into 11 million common shares. The preferred stock became convertible after a year of mandatory waiting period. Earlier this week, Air Liquide, the world’s second-largest industrial gas producer, converted half of the preferred stock into 5.5 million shares and sold them. It still owns the remaining 50% of the preference shares, a spokesman for Plug Power told Albany Business Review. That means Air Liquide made $32.02 million on the initial investment of just $1.3 million.

Air Liquide remains seated on Plug Power’s board

Air Liquide remains seated on the Latham, New York-based company’s board of directors. Citigroup Global Markets oversaw the Tuesday’s transaction. Plug Power CEO Andy Marsh has turned the company around, winning deals with Fortune 500 companies such as Wal-Mart Stores, Inc. (NYSE:WMT) and The Procter & Gamble Company (NYSE:PG). Air Liquide is also helping Plug Power expand its fuel cell and hydrogen businesses.

Plug Power shares fell 0.18% to $5.54 in pre-market trading Friday.