Facebook shares plunge in Wall Street

Facebook shares sank 11 percent in the first day of trading without the full support of the company's underwriters, leaving some investors down almost 25 percent from where they were Friday and driving others to switch back to more established stocks.

Facebook's debut was beset by problems, so much so that Nasdaq said on Monday it was changing its IPO procedures. That may comfort companies considering a listing, but does it little for Facebook, whose lead underwriter, Morgan Stanley, had to step in and defend the $38 offering price on the open market.

Even so, one source said Morgan Stanley's own brokers were at one point "ranting and raving" about glitches that left unclear what trades had actually been executed.

Without a fresh round of defence, Facebook shares ended down $4.20, at $34.03, on the Nasdaq. That was a decline of almost 25 percent from Friday's intra-day high of $45 a share.

Volume was again massive on Monday, with nearly 168 million shares trading hands, making it by far the most active stock on the US market. Nearly 581 million shares were traded on Friday.

The drop was so steep that circuit breakers kicked in a few minutes after the open to restrict short sales of the stock, according to a notice from Nasdaq.