SAN JUAN, Puerto Rico — A commission created to audit Puerto Rico’s debt is questioning the legality of government-issued bonds in a report released Thursday, saying the struggling U.S. territory might not be responsible for paying a portion of the money owed.

The report comes as the U.S. Congress is debating how best to help Puerto Rico as it struggles to restructure $70 billion in public debt. The island is widely expected to default on a $2 billion payment due July 1.

The commission, whose 17 members were in part appointed by Puerto Rico legislators, found in its pre-audit report that millions of dollars of debt might have been issued in violation of the island’s constitution. They say that is significant because previous court rulings have found that some U.S. municipal agencies were not responsible for paying debt if it was illegally issued.

The 44-page report says that Puerto Rico has borrowed more than $30 billion to finance deficits since as early as 1979, although its constitution prohibits it from doing so.

The constitution also bars the government from issuing loans for more than 30 years, but the commission found that the government has long done that. For example, a debt was incurred in 2014 to repay debt from 2003, which was used to refinance a 1987 debt.