Mortgage credit availability decreased in August as one originator decided to stop its whole loan purchase program, according to data released Thursday by the Mortgage Bankers Association.

The Mortgage Credit Availability Index fell 0.4% to 164.7 in August from the month prior, the MBA said. A decrease in the index signals a tightening of credit standards.

On a component basis, the indexes for confirming, government and conventional mortgage credit availability all dropped. The conforming MCAI dropped 0.9% over the month, while the government MCAI dipped 0.5% and the conventional MCAI slipped 0.2%.

The jumbo MCAI, meanwhile, rose 0.5% month-over-month.

"Credit availability decreased slightly over the month, driven by one midsized investor closing their correspondent operations," Lynn Fisher, MBA vice president of research and economics, said in a news release.

The MBA receives anonymized data from Ellie Mae in producing the index, a spokesman clarified.

"Despite the loss of all of the programs associated with this investor, the jumbo MCAI increased by 0.5%, indicating that credit conditions continue to ease among jumbo loan programs," Fisher said.