The bond market’s student-debt headache just got bigger -- almost twice as big, in fact, at least for investors who relied on an initial estimate from Fitch Ratings.

The credit-ratings company warned last week that $37.5 billion of securities tied to loans made under the Federal Family Education Loan Program face downgrades due to slow repayments that could push the bonds into technical default. There’s only one problem: the number was wrong.

In a corrected estimate, Fitch now says the value of bonds on review for downgrade is actually $71.2 billion, according to a release from spokeswoman Hannah James.

"The original announcement misstated the number, there was no impact on the ratings," James said.

The new estimate represents over 40 percent of the entire universe for bonds outstanding tied to government-backed FFELP student loans, and approximately 46 percent of those that Fitch grades, said John McElravey, Wells Fargo & Co.’s head asset-backed bond researcher.

The initial number “did seem low,” McElravey said in an e- mail Wednesday, adding that his clients had questioned the early tally.

Investors have scrambled this year as Fitch and Moody’s Investors Service warned that slow borrower repayments may force them to cut ratings on some bonds from AAA to below investment grade because of the risk that maturities will be breached. Estimates of the size of the problem have grown since the warnings.

Deutsche Bank AG, relying on a set of new ratings criteria proposed by Fitch, calculated last month the problem was probably in the range of $60 billion. They acknowledged the scope could grow “substantially,” based on the bond graders.

Market participants have until Dec. 31 to comment on Fitch’s proposed ratings criteria.