Investor Warren Buffett says distracted driving appears to be a growing problem on American roads that contributed to an increase in deaths last year and hurt profits at his company's Geico insurance unit.

Buffett said on CNBC Monday that auto insurance rates are going up this year because of the increased occurrence and severity of accidents last year.

The National Safety Council recently estimated the number of traffic deaths in the United States rose 8 percent from 2014 to 2015, the largest year-to-year percentage increase in a half-century.

Over the weekend, Buffett released his annual letter to Berkshire Hathaway shareholders. Geico's underwriting profit plummeted to $460 million last year from 2014's $1.16 billion.