A large number of trades in general-obligation bonds issued by Puerto Rico earlier this month have been canceled by dealers, Bloomberg reports. The news follows an announcement Monday from the Financial Industry Regulatory Authority that it is examining trading activity surrounding the bonds.

On March 11, Puerto Rico sold $3.5 billion of debt in the biggest high-yield offering the $3.7 trillion municipal market has ever seen. This deal gave the self-governing U.S. territory enough cash to pay its bills through June 2015. The tax-free bonds are due to mature in July 2035, and they are expected to yield around 8.73 percent, Bloomberg reports.