U.S. prosecutors are investigating whether the founder of the bankrupt private-equity firm Abraaj Group bribed senior politicians in Pakistan, according to people familiar with the matter.

Arif Naqvi was arrested by U.K. police in London in April after U.S. prosecutors indicted him on charges of fraud. Dubai-based Abraaj was the largest private-equity firm based in emerging markets before it collapsed in 2018. Mr. Naqvi was freed on bail and placed under a 24-hour curfew in his London apartment awaiting a trial to decide whether...