Home builder Beazer Homes USA Inc said on Friday it received purported default notices related to some senior notes from the bank that serves as trustee for the notes, sending shares down as much as 15 percent.

Beazer, already facing a deteriorating U.S. housing market as well as two separate pending probes related to its mortgage-origination business, said it believes the notices of default are invalid and without merit.

U.S. Bancorp, parent of U.S. Bank, declined immediate comment.

Last month, Beazer sued U.S. Bank, the trustee for the senior notes, in federal court in Atlanta, asking the court to rule that a delay in filing its quarterly financial report did not constitute a default on $1.3 billion of its outstanding notes.

As a trustee, U.S. Bank acts as middleman between Beazer and its bondholders, providing administrative services such as distributing interest payments. It also passes on notices of default if certain conditions are not met. The bank does not necessarily have lending exposure to Beazer.

U.S. Bank said in the notices that Atlanta-based Beazer is in default because it has not yet filed its quarterly report for the period ended June 30. The notices allege the defaults will become events of default if not remedied within 60 days, Beazer said.

The home builder said its agreements related to the notes require delivery of quarterly reports to U.S. Bank within 15 days of their submission to regulators. It previously said it had delivered every quarterly report as required and never missed a bond payment.

Beazer said on August 15 its delay in filing its third-quarter Form 10-Q was due to internal probes into the company's mortgage origination business.

It said last month its former chief accounting officer, who was fired, may have caused reserves and other accrued liabilities to have been recorded in prior accounting periods above what is allowed under generally accepted accounting principles. The company said resolution of the issue would not affect its reported cash position.

In July, Beazer disclosed the SEC was investigating possible violations by the company of U.S. securities laws.

Earlier this year, Beazer disclosed it was the subject of several lawsuits as well an informal SEC probe and a U.S. Attorney's investigation into practices in its mortgage business.

On Friday, Beazer's shares fell as low as $9.50, before easing to $9.90, down $1.01, or 9.3 percent, in early trading on the New York Stock Exchange.

(Reporting by Ben Klayman)