(Reuters) - Facebook Inc will close the books on its mammoth $10.6 billion initial public offering Tuesday, according to a source familiar with the deal.

The No. 1 social network is scheduled on Thursday to price its shares, which begin trading on Friday. It has stopped taking orders for the IPO two days ahead of schedule.

The IPO is already oversubscribed, which is why the social network is closing its books earlier than expected.

No decision has been made about raising the proposed offer price for Facebook shares, which are being offered at $28 to $35 each, said the source, who asked not to be identified because discussions with the company are private. If the price range is increased, it will likely be done after final orders come in Tuesday. Given the size of the IPO, the deal's underwriters are likely to be very cautious about raising the price range, the source said.

A host of Wall Street banks are underwriting Facebook's offering, with Morgan Stanley, JPMorgan and Goldman Sachs serving as leads.