The much-anticipated initial public offering was delayed by a half hour on Friday because of glitches, and there are now suspicions of illegal activity.
U.S. regulators want to know if big investors at Morgan Stanley were tipped off about a negative report on Facebook's finances. That's information regular investors didn't get.
A Senate panel is reviewing the allegations, the U.S. Securities and Exchange Commission is investigating and the state of Masschusetts has subpoenaed the bank.
"Did all prospective investors get all the same information at the same time? Or were there certain preferred investors given special information which gave them an advantage or an edge here?"questioned Massachusetts' Secretary of State William Galvin.
The company's stock is down almost 20 percent just days after Facebook hit the market, and now shareholders are suing, alleging the online social network hid their slowing revenue projections.
Also, regulators may be focusing on another matter: Did Facebok decide to sell 25 percent more stock than they originally told the public they would? According to the Wall Street Journal, the company's CFO apparently added that additional stock expecting more people would want to buy shares of Facebook.
ABC News contributed to this report.