The number of people in the United States who consider themselves to be of more than one race has surged by nearly a third over a decade, the US Census Bureau said Thursday.

In an analysis of the 2010 national census results, it said nine million people reported themselves to be of multiple racial origin, up 32 percent from the 2000 census.

The biggest combinations included white and black (1.8 million), white and "some other race" (1.7 million), white and Asian (1.6 million), and white and American Indian and Alaska Native (1.4 million).

Three states -- California, Texas and New York -- each had a multiple-race population of at least 500,000 people.

"These comparisons show substantial growth in the multiple-race population, providing detailed insights to how this population has grown and diversified over the past decade," said Nicholas Jones of the Census Bureau's racial statistics branch, in a statement.

The 2000 census was the first to give respondents the option of identifying themselves with more than one race. The 2010 census put the nation's overall population at 308,745,538 as of April 1 that year, up 9.7 percent from 2000.