LOS ANGELES, Calif. — L.A. County Sheriff Lee Baca is scheduled to be interviewed today by federal prosecutors examining allegations of abusive conduct by sheriff’s deputies at L.A. County jails and other problems in his department, although the sheriff says he is not an investigation target, a newspaper reported.

Baca’s scheduled interview with federal prosecutors marks an important milestone in an investigation that has spanned more than 18 months and involved federal authorities questioning inmates, jailers and high-ranking sheriff’s managers.

Part of the federal inquiry centers on whether sheriff’s officials obstructed an FBI investigation into allegations of deputy misconduct at L.A. County jails, according to the newspaper.

The obstruction probe may dwell on indications that sheriff’s officials sought to hide a Men’s Central Jail inmate who the FBI had enlisted to collect information on allegedly abusive and corrupt deputies. In an unusual move, sheriff’s officials responded by moving convicted bank robber Anthony Brown to a different jail under fake names, The Times reported.

The officials assigned at least 13 deputies to watch Brown around the clock, according to documents reviewed by The Times. Once the operation was over — it was codenamed Operation Pandora’s Box — the deputies received an internal email thanking them for helping “without asking to (sic) many questions and prying into the investigation at hand.”

Whether Pandora’s Box was intended to protect the inmate, as a sheriff’s spokesman asserts, or neutralize him as an FBI informant is a key issue in the federal investigation into brutality in the jails, according to The Times.

Four sheriff’s officials told The Times that Baca played a significant role in the operation: After learning that an inmate in his jails may have been working as an FBI informant, Baca called a meeting and gave his staff orders on how to handle the situation. One of the four officials said Baca continued afterward to guide the operation and get updates.

In an interview this week with the Times’ Editorial Board, Baca said he’s been assured he’s not a target of the FBI investigation.