TuSimple Holdings Inc. co-founder Mo Chen has taken control of the self-driving trucking company as federal authorities continue to investigate TuSimple's relationship with Mr. Chen's other startup, a Chinese hydrogen-trucking company. A TuSimple filing with the Securities and Exchange Commission on Wednesday shows that Mr. Chen has 59% of the voting power at the San Diego-based company, giving him control as of Nov. 9, a day before the company announced it had ousted its board of directors. Mr. Chen acquired the stake through stock purchases using his family trust and British Virgin Islands-based entities, according to the securities filing. TuSimple's newly appointed chief executive officer, Cheng Lu, said, "We have a strong sense of urgency to put our company back on track and regain trust from all stakeholders." A weekly digest of tech reviews, headlines, columns and your questions answered by WSJ's Personal Tech gurus.