As Facebook shares continued their slide, regulators launched inquiries into whether privileged Wall Street insiders were alerted to the company’s weakening financial projections, leading them to shun the stock or dump shares just as buying was opened to the public.

Morgan Stanley, which led the Wall Street effort to bring the social network public, came under fire following reports that the bank had told some favored clients that the bank was cutting its revenue estimates for Facebook. The lowered expectations came after the tech giant expressed caution in a public filing about its advertising sales on mobile devices.

The legal issue raised could be “securities fraud — plain and simple,” said Ernest Badway, a securities lawyer in New York and New Jersey and a former enforcement attorney at the U.S. Securities and Exchange Commission. “You can’t be putting out two sets of numbers.”

SEC Chairwoman Mary Schapiro said the agency will examine “issues” into the bungled Facebook public offering. The Financial Industry Regulatory Authority, the Wall Street industry-funded watchdog, has also expressed concern, and Massachusetts securities regulators have issued subpoenas for Morgan Stanley.

“If true, the allegations are a matter of regulatory concern to FINRA and the SEC,” Rick Ketchum, the watchdog’s chairman and chief executive, said in an e-mailed statement.

One major institutional investor was informed of the lowered expectations during Facebook’s IPO “roadshow,” in which Morgan Stanley and other underwriters appeared before mutual funds and other big investors to make the case to buy shares in advance of the public offering.

“I am pretty sure the grandma who bought 10 shares of Facebook through her Schwab account didn’t get that memo,” said a person familiar with the matter who declined to be named to preserve his business relationship with Wall Street investment banks.

Facebook’s offering was one of the most hyped events on Wall Street, and became the biggest tech IPO in history. The company raised $16 billion by listing on the Nasdaq Stock Market in a move that valued the company at $104 billion, which is bigger than American corporate stalwarts such asMcDonald’s Corp. andAmazon.com Inc.

But since the first few minutes of trading on the Nasdaq just a few days ago, Facebook’s life as a public company has been tumultuous.

Facebook’s shares were delayed by two hours on its first day of trading, and investors complained of glitches in confirming that trades even took place. Shares never finished the first day of trading with a big surge, and have plunged 26% since Friday.

Facebook’s stock lost $3.03 on Tuesday, or 9%, closing at $31, down sharply from its IPO price of $38.

Securities lawyers said the IPO’s problems could invite lawsuits from angry investors and others against their brokers, Nasdaq, Morgan Stanley and potentially even Facebook.

“It’s a disaster,” Badway said. “I just can’t believe they screwed up so badly.”

Facebook declined to comment.

Nasdaq has set aside more than $13 million to deal with potential claims against the exchange, said Credit Agricole Securities analyst Rob Rutschow. He said there is fear that “Nasdaq has tarnished its reputation with potential companies looking to IPO, and that additional legal costs are possible.”

The legal backlash has already begun. On Tuesday, Maryland investor Phillip Goldberg sued the stock exchange in federal court in New York, accusing it of failing to timely execute trades, causing him and others to lose money. The suit seeks class-action status.

Regulators also are putting the trades and the Wall Street players under scrutiny.

The Massachusetts Secretary of State, which regulates the securities industry in that state, issued subpoenas to Morgan Stanley regarding the bank’s analyst discussions with “certain institutional investors about the revenue prospects for Facebook” before last week’s IPO.

In Washington, SEC Chairwoman Schapiro said the agency needed to examine issues raised by Facebook’s IPO.

“I think there is a lot of reason to have confidence in our markets and in the integrity of how they operate, but there are issues that we need to look at specifically with respect to Facebook,” Schapiro told reporters.

Morgan Stanley defended its actions, saying it was “in compliance with all applicable regulations.”

The bank added that “a significant number of research analysts” in the syndicate of banks taking Facebook to market “reduced their earnings views to reflect their estimate of the impact of the new information. These revised views were taken into account in the pricing of the IPO.”

Several Facebook investors said their trust in the stock market was shaken by their experiences.

Niels Hansen, a 40-year-old software engineer from Murrieta, said it took him several hours Friday to determine whether his order for 100 shares at $42 had gone through.

He said all he could determine from his TD Ameritrade online account was that the order was “pending.” So Hansen placed a second order for 100 shares at $39. It turned out that both orders went through — and so far the value of his investment has lost $3,000. He has held on to the shares.

“I didn’t want to be left out, so I ended up getting stuck,” he said. “I kept hitting ‘cancel, cancel,’ but it wasn’t able to cancel.”

TD Ameritrade said in a statement that a “small percentage” of its clients reported difficulty trading Facebook stock Friday.

Randy Wilk, 52, a real estate property manager from Oakland, said he placed an order through a broker for 230 shares but that it took four hours to discover the trade was executed at $42 a share. By that time, the stock’s price had fallen back to the opening price. Wilk said he sold the shares Tuesday at a loss of about $2,500.

“This had to be the most disastrous IPO in history,” Wilk said. “It was the most miserable experience I’ve had as an investor.”

Jessica Guynn and Jim Puzzanghera of The Times’ staff contributed to this report.