"The Securities and Exchange Commission is investigating the events leading up to the collapse of Bear Stearns Cos., specifically a surge in options contracts betting that the investment bank's share price would drop precipitously, according to people familiar with the matter....
The unusual trading in Bear's options began as early as March 7 and escalated through the following week...."Betting on a 57% decrease in Bear Stearns stock in nine days is very unusual," said Todd Salamone, senior vice president of research at Schaeffer's Investment Research."
Last week, the number of open put options leaped from 167,439 at the open of trading on Monday to 465,820 by the following Monday. That compares with open put contracts on Bear Stearns hovering around 155,000 the previous week, according to data from Schaeffer's Investment Research Inc., an options-research firm in Cincinnati.
This is really not much to go on as many believed there could be trouble, but still I guess few (if anyone) expected this large of drop.
BTW there is also an investigation into the words of Bear executives prior to the collapse. From the NY Times:
"According to the Associated Press, the S.E.C.’s enforcement arm has sent a letter to JPMorgan Chase, which has offered to buy Bear Stearns, discussing “investigations and potential future inquiries into conduct and statements by Bear Stearns” before the takeover was announced."