NEW YORK (TheStreet) -- Shares of Voltari (VLTC) were gaining 173.3% to $2.76 on heavy trading volume Wednesday after activist investor Carl Icahn disclosed a stake in the mobile ad company.

Icahn disclosed that he owns about 4.74 million shares of Voltari, giving the investor a 52.3% stake in the company.

The disclosure of Icahn's stake in Voltari comes after the company announced the closing of a rights offering which gave shareholders the option to buy up to 4.3 million shares of common stock in the company. The company received net proceeds of $4.6 million from the rights offering.

About 3.4 million shares of Voltari were traded by 10:03 a.m. Wednesday, well above the company's average trading volume of 56,000 shares a day.

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