The U.S. Federal Trade Commission cleared Facebook Inc's acquisition of Instagram, voting unanimously to close its antitrust investigation into the deal without taking any action.

The move frees Facebook to complete its purchase of the mobile photo application maker, the biggest acquisition in its history. Facebook announced plans to buy Instagram in a cash and stock deal for $1 billion in April.

Under the terms of the deal, Facebook will acquire Instagram for $300 million in cash and roughly 23 million shares of Facebook common stock.

The deal is currently valued at $747.1 million, based on the $19.44 closing price of Facebook's shares on Wednesday.

Shares of the world's No.1 online social network have declined roughly 50 percent since the company's highly-anticipated initial public offering in May. Slowing revenue growth and a flood of insider shares that could hit the market in the coming months are among investors' key concerns.

The Instagram application, which allows users to add filters and effects to pictures taken on their smartphones, could bolster Facebook's mobile efforts -- an area that is considered something of a weak spot for the company.

The deal also ensures that the fast-growing mobile app, which said it had 80 million users in July, will not fall into the hands of a Facebook rival such as Twitter or Google Inc.

Still, the price that Facebook paid for the two-year-old company, which doesn't have any revenue, stunned analysts and investors.

Facebook said in its most recent 10Q regulatory filing that it plans to maintain Instagram's products "as independent mobile applications to enhance our photos product offerings and to enable users to increase their levels of mobile engagement and photo sharing."

Facebook did not provide a further update on the timing of the deal on Wednesday, but said it was pleased the FTC has cleared the transaction.

Facebook had initially said it expected the deal to close in the second quarter, but later changed the time frame, saying it expected the deal to close by the end of the year.

Facebook is scheduled to appear at a so-called "fairness hearing" before the California Department of Corporations on August 29.

The hearing, which provides California-based companies with an alternative to registering shares with the Securities and Exchange Commission, could expedite the transfer of Facebook shares to Instagram, potentially making it possible for the deal to close as soon as next week.