The probe is focusing in particular on how trading was handled on the first day the company went public, a report from The Wall Street Journal says.
CEO Dara Khosrowshahi sent a letter to employees after Uber's messy IPO last Friday, comparing the road ahead to what Amazon and Uber faced post-IPO.
Uber is set to begin trading Friday morning in one of the largest tech IPOs ever. Here are some photos from the traditional bell-ringing ceremony.