Six California residents face fraud and conspiracy charges in an alleged scam in which investors were promised a stake in a fictitious oil and gas project on Montana's Fort Peck Indian Reservation.

The first of the suspects, Mike Campa of Yorba Linda, Calif., made an initial appearance Tuesday in U.S. District Court in Great Falls. Assistant U.S. Attorney Carl Rostad says Campa did not enter a plea and he plans to hire his own attorney.

The six defendants were arrested by authorities Aug. 24 in California. Rostad says formal charges are pending.

An affidavit submitted by an FBI agent in the case shows that beginning in 2009 dozens of people across the country invested about $673,000 into a drilling project in the Bakken oil patch that authorities say was bogus.