Updated from 4:58 p.m. EDT

Biogen Idec ( BIIB) is in play.

Ending months of speculation, the Cambridge, Mass.-based biotech firm confirmed late Friday that it has received "expressions of interest" from third parties interested in acquiring the company.

One of those interested parties is famed investor Carl Icahn, according to a statement released by the company. The statement didn't make clear if Icahn had presented a specific buyout offer to Biogen Idec's board, or if Icahn was pressing the company to put itself up for sale.

Icahn owns 2.74 million shares, or about 1%, of Biogen Idec. In late August, the Federal Trade Commission approved Icahn's request to purchase more of the company. How much more he purchased, if any, has not been disclosed.

Shares of Biogen Idec shot up nearly 17% in recent after-hours trading to $81.10.

Biogen Idec's statement is somewhat cryptic in that it doesn't detail any specific acquisition offer. Instead, the company said its board of directors "authorized management to evaluate whether third parties would have an interest in acquiring the company at a price and on terms that would represent a better value for its stockholders than having the company continue to execute its strategy on a stand-alone basis."

Biogen Idec spokeswoman Amy Reilly explains that the board is asking management "to explore strategic alternatives" for the company. She declined to offer any more specifics, including the role that Icahn is playing.

Biogen Idec has hired Goldman Sachs and Merrill Lynch as financial advisers.

The subject of Biogen Idec's potential as an acquisition target has been hotly debated ever since Icahn revealed his stake. Large pharmaceuticals firms are widely believed to be eyeing fast-growing biotech firms as a panacea for their operating ills, caused mostly by the loss of revenue from blockbuster drugs coming off patent protection.

Earlier this year, AstraZeneca ( AZN) acquired biotech firm MedImmune for $15.6 billion.

However, there are contractual issues that could make any deal with Biogen Idec complicated.

Biogen Idec and Genentech ( DNA) share rights to the blockbuster cancer drug Rituxan. Under terms of the agreement, any "change of control" at Biogen Idec triggers Genentech's right to purchase 100% of Rituxan.

Biogen Idec also shares rights with Irish drug maker Elan ( ELN) to the multiple sclerosis drug Tysabri. Again, if there is a change of control at Biogen Idec, Elan has the option to buy 100% rights to Tysabri, although Elan may not be financially strong enough to do so.

To see all of Icahn's stock holdings, check out the Carl Icahn portfolio at Stockpickr.com.

Adam Feuerstein writes regularly for TheStreet.com. In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet.com. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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