The Federal Deposit Insurance Corp. has fined a pioneer of the fintech-bank partnership model more than $600,000 over alleged misdeeds by one of its marketplace-lending affiliates, a stark reminder that regulators are closely watching the burgeoning industry.

Cross River Bank, a New Jersey institution that works with more than a dozen marketplace lenders, found itself in the FDIC’s crosshairs after an examination report in 2015 found its partner Freedom Financial Asset Management LLC had misled consumers on the terms of its debt-consolidation services.