Rancho Santa Margarita-based CalWest Bancorp reported a loss of $757,000 for the third quarter, compared with net income of $300,000 a year earlier. The loss in the latest quarter was driven primarily by provisions for a single loan.

The holding company of South County Bank N.A. registered net interest income of $983,000 but set aside $850,000 as a cushion against a distressed $2.6 million loan. The bank said it is in negotiations with the borrower, but felt it was “prudent to record the provision based on the deterioration of the commercial real estate collateral.” That left the bank with $133,000 in interest income, compared with $1.2 million for the same quarter a year ago, when the bank did not set aside any provisions.

CalWest’s noninterest income totaled $615,000, down 20% from a year earlier.

The company had about $151.6 million in assets as of September, about a 2% drop from a year ago.

Total loans at the end of the third quarter were $70.3 million, down 11% from last year. Loans currently represent about 47% of the bank’s total deposits.

The company saw a loss of $588,000 for the first nine months of this year, wider than the loss of $394,000 for the same period a year ago.