New York City expanded its bond offering a second time to meet demand for tax-exempt debt with the highest credit ratings in the city’s history.

The most populous American city yesterday offered securities due from 2021 through 2026, boosting its fixed-rate sale by 8% to $919 million. Bonds set to mature in 19 years were priced to yield 4.51%, 0.09 percentage point more than the Municipal Market Advisors index of toprated bonds.

New York, borrowing to refinance higher-interest bonds dating as far back as 1997, increased the size of its offering by 21% Tuesday from the original $700 million as underwriter Morgan Stanley set prices for institutions such as funds and insurers. During the two previous trading days, the city got $359 million of orders from individual investors, its second-highest ever, according to a statement Tuesday.

“It could be that they were surprised by the demand,” a senior analyst at the Concord, Massachusetts-based independent research firm that compiles Consensus yield indexes, Matt Fabian, said.

The city initially sold fixed-rate bonds due from next year through 2021, then added the longer maturities yesterday. As part of a larger refinancing, New York also plans to sell auction-rate bonds on or about August 9 in four $100 million pieces.

General obligation bonds issued by the city of 8.2 million people carry ratings of AA, Aa3 and AA- from Standard & Poor’s, Moody’s Investors Service, and Fitch Ratings, respectively.