PORTLAND, Ore. (KOIN 6) — A secret grand jury indictment was unsealed today revealing new details about an alleged sex trafficking operation.

The 53-count indictment identifies the four suspects as Dedrick Wayne Thompson, Brandy Cheri Wilson, Joshua Daniel Carter and Floyd Duane Luster Jr. All four are in police custody.

Thompson and Wilson face the bulk of the charges. Both are accused of compelling prostitution. Court documents show they used force and intimidation to compel a female to engage in prostitution or attempted prostitution. The two are also charged with promoting prostitution.

Court documents and Portland police say the case involves four females who were victims of sex trafficking that began in Oct. 2013 and continued until February 2015. One of the four victims was under the age of 18 when authorities say Luster compelled her into prostitution, according to court documents.

Thompson is accused of causing physical injury to one of the four victims when he choked her throat, court documents state.

Carter is accused of helping to promote the acts of prostitution, court documents state. His specific role in the case has not been released by police or prosecutors.

The grand jury issued 11 total counts of tampering with a witness between Thompson and Luster. In December 2014, a separate secret indictment was filed against Thompson and Wilson. In that case, Thompson is accused of using force and intimidation to compel a separate female into prostitution that occurred between Jan. 2012 and Nov. 2014. Wilson is alleged to have been helping promote the prostitution, court documents state. The female victim in that case is now the subject of the most recent witness tampering charges filed against Thompson and Luster.

Court records show the victim compelled into prostitution back in Jan. 2012 was also physically assaulted by Thompson. He has been convicted of 11 felonies, one misdemeanor and six probation violations, according to court records. Thompson was convicted in federal court of knowingly taking receipt of a stolen firearm, court records show.

A court date will be set for all four suspects later this month to determine a trial date.