NEW YORK – Facebook’s shares opened 11 percent higher, but soon struggled to stay above their $38 offering price. More than 30 brokerages and banks were involved in the offering, which saw a nearly 571 million shares change hands on Friday – a record for a stock debut.

The Internet company’s shares opened Friday around $42 and within the first half hour fell as low as $38. The stock recovered as underwriters stepped in to support the price, according to people familiar with the matter. But in the final hour of trading, the shares lost steam and fell back to the $38 level.

The debut was marred by a 30-minute delay in the opening of the shares, coupled with reports from traders about lack of communication about orders. Nasdaq officials told exchange members in a notice at noon that its staff was “investigating an issue in delivering trade execution messages” from trades made in Facebook’s IPO. Around 1 p.m. Nasdaq indicated it would provide a “manual report” to brokers with information on Facebook trades.

Once the stock opened, trading was robust?100 million shares traded in the first few minutes and more than 200 million shares changed hands in the first hour. The record for most shares traded on the day of an IPO had been held by General Motors Co., GM -1.99 percent at 458 million.

But during the delay, and afterwards, traders said they were having trouble changing or canceling orders they had submitted to Nasdaq’s queue starting at 7:30 a.m.

Traders said the orders were accepted normally, but the usual process for canceling or altering an order wasn’t accepted, suggesting problems with the queue.

One person familiar with public offerings called Facebook’s a success, saying that, the delay aside, the trading indicated the stock was well priced. The person said big one-day pops are far-less common in large offerings where lots of trading can help keep pricing efficient.

Social media stocks are among the day’s biggest losers. Online games maker Zynga Inc. ZNGA -13.42% shares dropped 13 percent to $7.17 and have been halted after hitting a single-stock circuit breaker. The stock fell more than 10 percent in five minutes, prompting the halt. Zynga is closely tied to Facebook, as 11 percent of the social network’s revenue comes from Zynga.

Facebook and its stockholders are selling about 20 percent of the company’s common stock in the IPO. By way of comparison, Groupon Inc. GRPN -6.69 percent sold about 6.3 percent of its stock in its IPO, according to Dealogic, while LinkedIn Corp. LNKD -5.65 percent sold 9.5 percent.

a>>