The problem, she and others say, is that the funds and firms representing bondholders are maneuvering behind the scenes to protect their stakes. But unlike an investor buying up a stock of a company, they do not have to reveal the amount or the type of investment they are making. That has made it harder to come up with a coherent negotiating strategy.

Until just a few years ago, hedge funds showed little interest in municipal bonds, which were seen as stodgy and safe — something for widows and orphans, not sophisticated investors willing to take big risks. That has changed in the last few years, as large local governments like Detroit and Jefferson County, Ala., were crushed by their debts.

Hedge funds that might not have bothered with public finance in the past found that they could scoop up distressed municipal bonds at a deep discount, as traditional investors in the bonds bailed out. They could then participate in the restructuring agreements that followed. In some cases, market analysts said, they played a useful role when they did so, because they provided liquidity that would otherwise not have existed.

Ms. Velázquez sees it differently.

“It has become increasingly clear that hedge funds, which have purchased a sizable part of Puerto Rico’s debt, are exacerbating the crisis and profiting from the island’s misery,” she said in a statement on Wednesday after introducing her bill. In her view and that of others, the unwillingness of investors to renegotiate their bond payments is forcing Puerto Rico to lay off teachers and nurses and reduce other kinds of government services.

“Rather than working to help resolve Puerto Rico’s financial crisis in a fair, orderly fashion, these funds are lobbying to cut basic services that 3.5 million American citizens in Puerto Rico rely on,” she said.

Puerto Rico’s $72 billion debt is complex, coming from almost 20 different governmental issuers and sometimes involving guarantees or other special features. It also has different types of investors whose interests are not necessarily the same, and it is difficult, if not impossible, to determine which types of investors now hold which types of debt.

Ms. Velázquez’s bill takes aim at federal regulations that require hedge funds and other investors to file statements with the S.E.C. only after they have acquired more than 5 percent of a class of a company’s stock. Her bill would lower the threshold to just 1 percent. In addition, it would establish a quarterly reporting requirement for the purchasers of bonds — including municipal bonds — as well as stock, to bring their under-the-radar activities into the light.