Eight years after mortgage-finance titans Fannie Mae (FNMA)  and Freddie Mac (FMCC) were seized by the U.S. government during the financial crisis, their hammerlock on the business of packaging home-loans into bonds is finally facing competition.

JPMorgan Chase  (JPM - Get Report) , the biggest U.S. lender, last month sold $2.65 billion of bonds backed by top-quality mortgages, following a $1.9 billion sale in March. Both bond deals consisted entirely of JPMorgan-originated home loans, and they didn't carry a guarantee from Fannie or Freddie, a common feature of almost all previous deals.

The latest transactions are a result of increasing demand from both banks and investors for high-yielding assets at a time of shrinking returns on government bonds. JPMorgan also is taking advantage of regulations that make it less costly to hold mortgage bonds than the underlying loans.

A third factor is that regulators have pushed Fannie and Freddie to more than double their fees for guaranteeing mortgages, making it more expensive for banks to rely on the government-sponsored companies for funding. Since at least 2012, the Federal Housing Finance Agency, which oversees the companies, has pushed for higher charges to encourage banks to provide more private financing for the mortgage market.

"It is a significant development," said Deepika Kothari, an associate managing director at Moody's Investors Service. "It's mostly driven by economic incentives, and the profitability situation that banks are operating under."

If more banks follow suit, the so-called "private-label" mortgage bonds could represent a new source of financing in a housing market that's been dominated for decades by the government-sponsored companies, Kothari said. (It should be pointed out that JPMorgan's $4 billion-plus of recent transactions represents a drop in the bucket, however: Fannie provided $516 billion of liquidity to the mortgage market in 2015 through loan purchases and bond guarantees, while Freddie provided $792 billion.)

Banks have been adjusting to post-crisis regulations that require them to hold more capital, which is the buffer of extra assets that's supposed to protect depositors in the event of steep losses and -- in the worst case -- head off costly and politically unpopular government bailouts. That means a key job of bank executives is to find high-earning assets that require as little capital as possible: Less capital means banks can finance their assets with borrowed money -- a way of boosting profitability.

Under regulations in place since the crisis, a typical $2 billion mortgage bond would require a bank to hold just $39 million of capital, versus $100 million for a portfolio of home loans, Moody's estimates.

At the same time, Fannie and Freddie have increased their fees for guaranteeing mortgages to an average 0.59% in 2015, up from about 0.26% in 2011, according to a federal housing finance report this month. Spokesmen for the two companies didn't respond to requests for comment.

JPMorgan's recent transactions were so unusual that the New York-based lender's CFO, Marianne Lake, was asked about them in July on a conference call to discuss the $2.47 trillion-asset lender's quarterly results.

"We're looking at more securitizations in the mortgage space," Lake said. "In doing that, we're being able to get private capital to take the majority of the lower credit risk and get better capital treatment for ourselves." A JPMorgan spokeswoman declined to comment further.

JPMorgan's July bond deal was backed by 8,953 mortgages. About 55% of the total balance is from "conforming" mortgages -- those that would meet the criteria for sale to Fannie or Freddie -- and the rest consisted of jumbo mortgages, or those with high balances, typically above $417,000. In the March bond deal, fully 75% of the loans were conforming.

Fitch Ratings assigned triple-A ratings to $2.37 billion, or about 90%, of the bonds sold in July, citing the high quality of the mortgages as well as JPMorgan's track record as a lender. In order to attract investors, JPMorgan agreed to keep at least 5% of each class of the bonds.

"They're the first bank to issue post-crisis using their own collateral," Suzanne Mistretta, a senior director in Fitch's U.S. residential mortgage-backed securities group, said in an interview.

It's not clear yet whether other large banks will follow suit.

Bank of America  (BAC - Get Report)  spokesman Terry Francisco said in an e-mail that the Charlotte, North Carolina-based lender has evaluated JPMorgan's deals and has no plans at this time to pursue similar transactions. Spokesmen for Wells Fargo  (WFC - Get Report)  and Citigroup  (C - Get Report)  declined to comment.

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Any decision to ape JPMorgan's transactions would depend on whether a given bank was in a position to benefit from the capital relief, as well as whether it had lucrative alternatives for investing any capital that's freed up, according to Madhur Duggar, a senior credit officer at Moody's. Yet another consideration is whether a bank would be willing to trade the bonds -- a key consideration for investors who are contemplating a purchase, he said.

"Banks are looking at the structure, given that it's an innovation in the market," Duggar said.