A deadly California casino bus crash has focused federal regulators on the niche tour industry.

A member of the National Transportation Safety Board said crashes like the one Sunday that killed 13 people have become so common that the board is studying the tragedies for common threads.

Experts say the tours are often run by small mom-and-pop operators who have deals with casinos to ferry passengers there.

They say the tours tend to target older people in lower-income ethnic communities.

Many of those killed in the crash near Palm Springs were Latinos who boarded the bus in the Koreatown neighborhood of Los Angeles.

The bus tours have proliferated with the expansion of casinos in the U.S. Deadly crashes have happened from New York to California and Minnesota to Texas.