ST. PETER, Minn. (AP) - The results of an investigation into security problems at the Minnesota Sex Offender Program are so confidential that state officials won't even release them to attorneys prosecuting the men who escaped from their cells in April.

An attorney for one man involved in the escape believes the report could include information about the possible involvement of hospital staff members in the escape, according to a report Sunday in the Free Press of Mankato.

The Minnesota Department of Human Services ordered the investigation after Michael Benson and three other men escaped from the Minnesota Security Hospital on April 15 - the second escape in 13 months. Benson made it to Kansas City, Mo., before he was arrested a few days later; the other escapees were arrested that night.

While Benson was still on the run, his father, Dale Blue, was arrested and accused of helping the men escape from the facility. His attorney, Marsh Halberg, got those charges dismissed in a motion questioning the quality of evidence against Blue.

That motion also raised questions about security at the hospital. It cited reports that a hospital staff member supplied saw blades used to cut through a bar on a window in Benson's room. There was also evidence that indicated staff had searched Benson's room several times after he started the long task of cutting through the bars and that surveillance equipment had recorded another inmate's telephone conversation about escape plans.

But Halberg was unable to obtain a copy of the state investigation into hospital security concerns.

"Further evidence pertaining to the involvement of staff members may be within the internal investigation of the Minnesota Security Hospital, however the hospital is refusing to turn over that report," Halberg said in the motion. "Despite the embarrassment and sensitivity of disclosure of the hospital investigation, those records could well buttress the defense arguments."

Halberg's not the only one who can't get the report. Nicollet County Attorney Mike Riley, who is in charge of prosecuting the escapees, has twice requested and been denied the report.

David Rowley, legal manager for the Department of Human Services, wrote to Riley on June 27 that disclosing the report would jeopardize public safety by "increasing the risk of patient escape."

Except for an executive summary, contents of the report have not been shared outside the Minnesota Sex Offender Program, he wrote.