OMAHA, Neb.—Berkshire Hathaway Inc. said Friday that its insurance underwriting operating earnings plunged 70.6% in the first nine months to $261 million compared with the same period of 2010, reflecting losses related to derivative investments in recent months and catastrophes.

Berkshire's insurance investment income for the nine-month period sank 7.4% year over year to $2.73 billion. The company lost $903 million on investments and derivatives during this time frame, compared with a $507 million gain in the same period of 2010.

Within the insurance underwriting group, General Re Corp. reported an underwriting loss of $46 million during the first nine months compared with $384 million earned in the same period last year.

Berkshire Hathaway Reinsurance Group recorded an underwriting loss of $322 million in the first nine months of the year compared with $68 million lost in the same period last year. The Berkshire Hathaway Primary Group registered an underwriting gain of 26.3% year over year to $168 million in the first nine months of the year.

Operating earnings for Berkshire Hathaway overall, including units such as the auto insurer Government Employees Insurance Co, dba GEICO, edged up by 0.3% year over year to $8.11 billion in the first nine months.

Berkshire suffered losses of about $1.3 billion from several catastrophes during the first nine months of the year, particularly first-quarter events such as the March 11 earthquake and tsunami in Japan. During the comparable period of 2010, Berkshire lost around $500 million.

Third quarter insurance operating earnings surged 447.2% year over year to $1.09 billion, including $875 million from a reduction in estimated liabilities related to retroactive reinsurance contracts.

But insurance investment income in the third quarter fell 10.3% from that of a year earlier to $783 million. In the third quarter, Berkshire lost $1.53 billion on investments and derivatives compared with $202 million gained the same period last year.

Gen Re’s third quarter underwriting earnings fell 26.4% to $148 million from those of the same period of 2010, but the reinsurance group earned $1.38 billion in the third quarter compared with a loss of $237 million in the same period a year earlier. The Berkshire Hathaway primary group’s third quarter underwriting gain edged up 11.5% to $58 million.

In the third quarter, Berkshire’s overall earnings fell 36.8% year over year to $3.81 billion.