California Bank & Trust, San Diego’s largest bank with about $11 billion in assets and 27 branches in the county, reported first quarter net income of $19.7 million, down 38 percent from the first quarter of 2013.

The bank said the main factor in the big drop in profits was a one-time loss of $13 million caused by the sale of collateralized debt obligations in its investment portfolio.

Excluding the loans that CB&T assumed from two failed banks, its total loans grew by $505 million from the like quarter of 2013, and stood at $8.4 billion as of March 31.

Total deposits were $9.5 billion as of March 31, up by $147 million from Dec. 31, and up $188 million from the first quarter of 2013.

The bank, a subsidiary of Zions Bancorporation of Salt Lake City, reported having total risk-based capital of 14 percent at the end of March, compared with 13.98 percent for the like quarter of last year.