Nasdaq boss Robert Greifeld has said he is "humbly embarrassed" about the technical glitch that led to a delay in trading of Facebook shares on the New York exchange on Friday.
Trading was delayed by about 30 minutes due to late order cancellations, reports suggest.
Facebook shares ended the day at $38.23, just above the company's initial pricing of $38.
The offer price valued the site at $104bn (£66bn).
"This was not our finest hour," said Mr Greifeld. As a result of the glitch, a number of investors were unsure whether their buy and sell orders had actually gone through.
However, Mr Greifeld said that once the glitch had been fixed, trading had been "successful"
More than 566 million shares in the company changed hands, a record volume for US market debuts.
Investors will watch with interest as Facebook shares begin their second day of trading on Wall Street later on Monday after the disappointing 0.6% rise on Friday.
Some analysts suggested the share price would have fallen had it not been for underwriters stepping in to buy up stock.
Strong demand in the run-up to the flotation had led the company to increase both the price and the number of shares available for sale.
Other internet companies have had mixed experiences recently when they have started selling shares.
Online games maker Zynga's shares fell 5% on their first day of trading in December 2011. However, shares in business networking site LinkedIn more than doubled on their debut in May last year, while Groupon shares jumped 30% on their debut in November.
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