SAN FRANCISCO — Two Northern California men accused of sexually abusing a teen runaway and keeping her in a metal box on their marijuana farm pleaded not guilty on Friday to federal drug charges.

The men appeared in San Francisco federal court in shackles and jail garb and were returned to custody after a brief hearing.

Federal prosecutors have charged Ryan Balletto, 30, and Patrick Pearmain, 25, with growing more than 1,000 marijuana plants on a remote Lake County farm. Both men are also charged with coercing a 15-year-old runaway to help with their alleged operation.

Balletto denied the charges even though federal prosecutors allege in court documents filed Wednesday that he confessed.

"The government ... has a recorded, Mirandized confession by Balletto, a recorded statement from the minor victim, and multiple recorded statements from others who were working on the grow site," prosecutors wrote Wednesday.

Authorities in Lake County learned about the case when the Los Angeles Police Department advised that Balletto might have kidnapped the girl.

Deputies visited Balletto's home on April 29 to ask about the missing girl. She called authorities the next day to say she was OK and in Sacramento. LAPD investigators traced the call and police located the girl at a West Sacramento hotel, where authorities arrested Pearmain, a federal complaint said.

Officers then found "equipment consistent with sexual bondage and sadomasochism" and a towel with blood stains at Balletto's pot farm. The equipment included a rack "presumably used to attach a human to the device and immobilize them."

The girl told investigators she was locked in a 4-by-2-by-2-foot box. Holes had been drilled in the box, and water was run through it to wash her without letting her out, the complaint said.

Investigators found human hair inside the box, where prosecutors said the girl was imprisoned "on multiple occasions, for days." Hundreds of marijuana plants and several firearms, including AR-15-style assault rifles and body armor were found as part of the investigation.

Prosecutors described Balletto as an ex-Marine who was preparing for an extended battle.

"The presence of so many weapons on the grow site, including two assault rifles and eleven loaded 20- and 30-round magazines ... indicate that Balletto was prepared to engage in an extended gun battle," prosecutors wrote.

Both men have been charged with two marijuana-cultivation charges and a count of coercing a minor to help with their alleged operation. In addition, Balletto is charged with possessing several firearms "in furtherance of a drug crime," according to the federal indictment.

Prosecutors argued in Wednesday's filing that both men should be denied bail if they make a request for release before trial. Neither man has requested bail and both men are scheduled to return to court Aug. 21.

Balletto's attorney, Jodi Linker of the Office of the Federal Public Defender, wouldn't comment after Friday's hearing. Pearmain's lawyer, Robert Waggener, also declined comment.