A commission created to audit Puerto Rico's debt is questioning the legality of government-issued bonds and says the U.S. territory might not be responsible for paying part of the money owed.

The report issued Thursday comes as the U.S. Congress is debating how best to help Puerto Rico as it struggles to restructure $70 billion in public debt and braces for an anticipated $2 billion default on July 1.

The commission found in its pre-audit report that millions of dollars of debt might have violated the island's constitution. Officials say that's significant because previous court rulings have that found some U.S. municipal agencies were not responsible for paying debt in such cases.