The internal investigation is looking into whether the 26-year-old hotel heiress had access to a cell phone while other inmates had to wait in line to use pay phones.

The probe will also determine whether Hilton was given a new jail uniform, instead of a recycled one like most other inmates, and finally, whether she had her mail delivered by a captain. Most mail is delivered by inmate trusties.

The accusations of special treatment were brought by deputies that approached their department's union, the Association for Los Angeles Deputy Sheriffs.

The deputies' claims differ from the department's information, said Steve Whitmore, the spokesman for the L.A. Sheriff's department.

"The investigation is to get to the bottom of this. It will shed a light on what actually occurred," Whitmore said.

Earlier, the department was accused of giving Hilton special treatment when it released her for medical reasons after just three days in jail. She was ordered to return the next day to complete her sentence. She was released on June 26.

Whitmore stressed that it was always the goal of the department to treat Hilton like any other inmate.

Hilton was serving time for violating probation of an alcohol-related driving incident.