NORTH FORK, Calif.—The former chairwoman of an American Indian tribe that recently signed a deal to build a Central Valley casino has stepped down after being accused of violating internal tribal policies.

The North Fork Rancheria of Mono Indians plans to construct a $250 million casino on a plot of land along Highway 99, just north of the city of Madera.

Former tribal chairwoman Jacqueline Davis Van Huss helped negotiate the deal, which was approved Monday. The agreement still needs final approval from the U.S. Department of Interior and the state Legislature.

Elaine Bethel-Fink took over as tribal chairwoman after Van Huss resigned in mid-April. The tribe's attorney would not specify what policies she is accused of violating.