Claims that Paris Hilton had special treatment in jail are to be examined by the Los Angeles Sheriff's Department.
Paris Hilton was released early for good behaviour
The investigation will look into claims by sheriff's deputies that the heiress was given a mobile phone while other inmates had to queue for pay phones.
It will also determine whether the 26-year-old heiress was given a new jail uniform instead of a recycled one.
Hilton served 23 days of a 45-day jail sentence last month for violating probation on a driving ban.
She was released early from the Century Regional Detention Facility in Lynwood, California, due to crowded jail conditions and time off for good behaviour.
The allegations of preferential treatment were brought by sheriff's deputies who approached their union, the Association for Los Angeles Deputy Sheriffs.
They say she was given a new uniform, access to a mobile phone and had her mail delivered by a captain. Most mail is delivered by inmates.
Their claims differ from the department's information, said Steve Whitmore, the spokesman for the LA Sheriff's department.
"We're going to investigate it and get to the bottom of it and find out exactly what happened," he said.
The department was previously accused of giving Hilton special treatment when it released her for unspecified medical reasons after just three days in jail.
She was later ordered to return to jail by a court.