As the Puerto Rican debt crisis continues to unfold, mutual fund managers have been busy trimming their sails to reduce exposure to the commonwealth's crisis.

Over the past year, the number of funds with exposure to Puerto Rico has been pared to 29 — out of a pool of 562 municipal bond funds — from as many as 48 in June 2015, according to data from Morningstar and a study by Markov Processes International. Total dollar exposure has been cut as well, from about $9.9 billion last summer to $6.3 billion now.

The exposure issue is central to the debate now over what happens next. Island officials have been negotiating with Washington lawmakers for a bailout package, though that hasn't stopped the first wave of defaults from happening.

Puerto Rico missed a $367 million payment May 2 on its Government Development Bank notes, but municipal bond investors in general remain hopeful that there will be limited contagion.

"The majority of municipal bond mutual funds don't show exposure to Puerto Rico debt," Sean Ryan, a senior MPI research analyst, said in an interview. "It isn't really a systemic issue, which is one thing that investors should always be worried about. In this case, only a few are exposed versus the entire category."

The retreat from Puerto Rican debt positions has been strong: