The U.S. government's investigation into the collapse of Lehman Brothers Holdings Inc. has hit daunting hurdles that could result in no civil or criminal charges ever being filed against the company's former executives, people familiar with the situation said.

In recent months, Securities and Exchange Commission officials have grown increasingly doubtful they can prove that Lehman violated U.S. laws by using an accounting maneuver to move as much as $50 billion in assets off its balance sheet, which made it appear that the...