Once an investor darling, autonomous trucking company TuSimple Holdings Inc. (TSP.US) has driven into a new development lane with the latest report that the U.S. national security regulator is pursuing criminal charges against the company’s three top officials. The revelation marks the latest setback for a company that was once considered frontrunner in the race to bring self-driving trucks to the lucrative U.S. market.

TuSimple’s troubles all stem from a single allegation that emerged last November, involving the improper and possibly illegal transfer of technology to another China-based trucking company with strong connections to its founding team. TuSimple has provided an explanation for those transfers, which looks reasonable, though it took a while to provide the information.

But the action raised red flags on the company’s board, which said it was unaware of the interaction between the two companies and responded by firing TuSimple’s co-founder and top executive Hou Xiaodi last November. The revelations also raised red flags at the U.S. national security regulator, the Committee on Foreign Investment in the United States (CFIUS), which has been wary of TuSimple for a while due to its Chinese roots and large operation in China.