The U.S. Transportation Department’s inspector general said it is auditing purchases by employees after finding more than $150,000 in possible fraudulent transactions on government-issued cards.

Recent probes revealed “weaknesses” in the Federal Aviation Administration’s oversight of workers’ use of SmartPay cards, the office of the inspector general said in an e-mailed statement today.

The investigation will look at the adequacy of the department’s internal controls for the program. Transportation Department employees made more than $200 million in purchases with these cards last year, according to the inspector general’s notice.