As San Bernardino, Calif., moved toward bankruptcy this week, municipal bond analysts were questioning how widespread the fiscal distress may prove to be, but were not predicting a wave of defaults.

San Bernardino’s vote to authorize a bankruptcy filing came after filings this summer by the California cities of Stockton and Mammoth Lakes. Those cities were following Vallejo, which emerged from bankruptcy in 2011, after a three-year struggle to reduce its debts to investors, retirees and others.

“I don’t believe that this is the beginning of a tidal wave of insolvency across the country,” said Richard P. Larkin, director of credit analysis at the underwriting firm H. J. Sims. “I am worried, however, that this phenomenon may grow in California.”

Over all, investors in municipal debt showed little sign of concern about the woes of either California or any other states. On Thursday the interest rate on the highest-quality 30-year municipal bonds fell below 3 percent for the first time ever, according to Daniel Berger, a senior market strategist at Municipal Market Data.