HELENA, Mont. — Twenty-one American Indian reservations will be the focus of the next phase of a $1.9 billion program to buy fractionated land parcels owned by multiple individuals and turn them over to tribal governments, Interior Department officials said Thursday.

Government officials will work with tribal leaders to plan, map, conduct mineral evaluations, make appraisals and acquire land on the reservations from Washington state to Oklahoma in this phase, which is expected to last through 2015.